* [CVE-2026-80994][MODERATE 7.0] net: openvswitch: fix flow mask use-after-free on flow deletion
@ 2026-09-12 10:33 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-12 10:33 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-80994
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: openvswitch: fix flow mask use-after-free on flow deletion
Commit: 0ba5cbc2f049af94ec94ff6f64958545efc5eaa2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0ba5cbc2f049af94ec94ff6f64958545efc5eaa2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80994
Analysis date: Sat, 12 Sep 2026 06:33:26 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80994 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80994
The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.
The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.
Published priority for this report: MODERATE 7.0
Manual review required: YES
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-80994 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-80994 CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '6.5';DESCR 'An Open vSwitch flow deletion race can cause a use after free because ovs_flow_tbl_remove may schedule flow mask release through RCU before ovs_flow_cmd_fill_info finishes building the delete reply. The stale flow mask pointer can still be read in the same operation, and KASAN reports a slab use after free in __ovs_nla_put_key while formatting the netlink response. For the CVSS the PR:L is used for the paranoid score because reliable triggering may be possible by a local actor with delegated OVS flow control, CAP_NET_ADMIN in a container like environment, or control of a local Open vSwitch management service rather than full host root. The issue is not directly reachable by raw network packets, but it may be reachable through an OVS control plane that can request flow deletion. Impact is at least local denial of service via kernel crash and may include confidentiality impact because freed mask memory is read while constructing a netlink message. Integrity impact is limited because the patch does not show an arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6) YES READ LOCK DANGER INIT RACE UAF SKB KERNEL_PANIC_PLUS_UAF HARDWARE LINUS KPANIC DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
1. ActionableScore
* Raw conservative score: 3
* Conservative score: 5
* Applied conservative floor/cap: REAL UAF FLOOR 5 applied, 3 -> 5, because this is an active structured RCU lifetime UAF and the stale mask is consumed in netlink reply construction, not only an immediate cleanup fault.
* Raw paranoid score: 6
* Paranoid score: 6
* Applied paranoid floor/cap: none
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
Conservative signals:
* +2 Real UAF / active lifetime violation: `flow->mask` can be scheduled for RCU freeing by `ovs_flow_tbl_remove()` while `ovs_flow_cmd_fill_info()` later reads it through the still-live `flow`.
* +1 Reliable kernel crash / strong DoS: KASAN shows slab-use-after-free in `__ovs_nla_put_key()` / `ovs_nla_put_key()` during flow deletion reply construction.
* +1 Structured stale-object exploitation leverage: the stale object is an active Open vSwitch flow mask, and stale fields are consumed while serializing the flow key/mask into a netlink response.
* -1 Hard race / timing: the commit explicitly states a short race window where the RCU grace period must pass between removal and filling.
Paranoid additional signals:
* +1 Attacker-influenced active-object lifetime: an actor able to manage OVS flows can create flow masks and repeatedly request flow deletion, influencing both object state and lifetime transition.
* +1 Confidentiality plausible: the stale mask is read while building a netlink reply, so if freed memory is reused before serialization, limited stale kernel data exposure is technically plausible.
* 0 race penalty in paranoid score: repeated flow operations and GFP_KERNEL allocation latency make the short window still defensible for manual-review sensitivity.
Important non-awarded signals:
* +2 strong exploitation leverage not awarded: no controlled reclaim, object substitution, arbitrary read/write, callback control, or demonstrated LPE is established.
* Concrete repeated release/refcount signal not awarded: this is a stale read/use of `flow->mask`, not a second `put`/`free`/refcount mutation on the same dangling reference.
* Weak LPE not separately awarded: possible exploitation beyond crash remains unresolved, but no independent LPE primitive is shown.
* Extra availability not awarded: the crash/DoS is already counted once.
* Remote network reachability not awarded: raw packets do not directly trigger the vulnerable path.
* CLASS_A not used: the patch establishes a real UAF but not a controlled corruption or authorization-boundary bypass.
Repeated-release/refcount check:
* First release can end lifetime: not applicable to same-reference repeated release.
* Exact same reference survives to second release: not established.
* Second operation mutates lifetime/refcount: no.
* +1 Concrete repeated release/refcount awarded: no.
* Paranoid repeated-refcount leverage awarded: no.
* FLOOR 5 applied: yes, but due active structured stale use in reply construction, not due repeated release/refcount.
3. Reachability analysis
The trigger is through Open vSwitch generic netlink flow deletion handling, specifically `OVS_FLOW_CMD_DEL`. The likely attacker is a local control-plane actor that can create and delete OVS flows, such as an OVS management service, a process with relevant network administration rights, or a container/service context with delegated OVS control.
Host-admin-equivalent privilege is not positively established from the supplied patch alone, so `HostAdminRequired=UNKNOWN`. The operation often maps to CAP_NET_ADMIN-like control, but the supplied evidence does not fully resolve whether the complete trigger requires host/init namespace CAP_NET_ADMIN or can be performed with delegated or namespace-scoped authority in a given deployment.
`NamespaceScopedPrivilege=UNKNOWN` because Open vSwitch and network namespaces may be involved, but the supplied evidence does not prove that all required stages are namespace-scoped and attacker-obtainable below host admin.
There is no direct packet-processing trigger. The bug is control-plane reachable through OVS flow management, not through ordinary ingress network traffic. Prior privileged setup may exist in real deployments if OVS datapaths and management access must already be provisioned, but this is deployment-specific rather than proven as a mandatory host-root prerequisite.
The race is real and described as short. It is not purely theoretical because the commit includes a KASAN report and explains that allocation latency can allow the RCU grace period to pass before reply filling.
4. Primitive and severity interpretation
The exact primitive is an RCU lifetime use-after-free of `flow->mask`. The `flow` object remains available to the delete command path, but its referenced mask may have been retired and freed after `ovs_flow_tbl_remove()`. The stale mask is then consumed by `ovs_flow_cmd_fill_info()` and `ovs_nla_put_key()` while formatting the delete notification.
This is an active structured-object UAF, not fixed stale storage. The stale object is not merely a dead buffer touched by hardware or a shallow destructor-only pointer. It contains structured flow mask state used by Open vSwitch netlink serialization.
There is no concrete repeated release/refcount operation. This case is category A from the prompt distinction, ordinary stale use/read after lifetime end, not category B second lifetime/refcount mutation through a dangling reference.
Primitive class is CLASS_B. Demonstrated consequence is kernel crash / DoS. Plausible additional consequence is limited confidentiality impact if stale mask memory is serialized into a netlink response after reuse. Speculative consequences such as privilege escalation or arbitrary kernel read/write are not established.
`ImportantCandidate=YES` because this is a real active structured UAF in a network virtualization control-plane path, reported by ZDI, with stale structured data consumed beyond a trivial cleanup fault. It needs Important-vs-Moderate manual review.
`AutoDowngradeAllowed=NO` because automatically closing it as ordinary Moderate would discard an unresolved active structured UAF with potential disclosure surface. This does not mean CLASS_A or confirmed Important, but it should not be auto-downgraded.
Likely operational severity is Actionable Moderate, with Strong Important candidacy depending on whether review finds practical below-host-admin reachability, controlled reclaim, or reliable disclosure beyond crash.
5. One-sentence report phrase
An Open vSwitch flow deletion race can free `flow->mask` through RCU before the delete reply is built, causing a real use-after-free in netlink serialization that can crash the kernel and may warrant review for limited stale-memory disclosure.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Reason: explicit RCU UAF, active structured object, ZDI report, and possible stale data serialization into a netlink response make this unsafe for automatic downgrade, even though controlled reclaim and LPE are not demonstrated.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: net: openvswitch: fix flow mask use-after-free on flow deletion
Commit: 0ba5cbc2f049af94ec94ff6f64958545efc5eaa2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0ba5cbc2f049af94ec94ff6f64958545efc5eaa2
Commit description:
The commit in the Fixes tag below made so flow->mask free is scheduled
via RCU right after it is removed from the flow table. The pointer
stays in the flow structure and it can be accessible while in the same
RCU critical section. This is done to avoid requiring ovs_mutex for
the ovs_flow_free().
However, while removing the flow during processing of CMD_DEL, we do
not take RCU read lock before the removal, and ovs_flow_cmd_fill_info()
uses the flow->mask pointer afterwards. The RCU read lock is taken,
but it's already late at that point. The comment on that line
acknowledges that the lock is cosmetic and doesn't serve a real purpose.
This leads to use-after-free if the RCU grace period passes between
removal and the filling. It is a short race window, but it is there
and can lead to a real crash in case memory allocation for the info
takes a bit longer:
BUG: KASAN: slab-use-after-free in __ovs_nla_put_key
net/openvswitch/flow_netlink.c:1996
BUG: KASAN: slab-use-after-free in ovs_nla_put_key+0x2463/0x2e30
net/openvswitch/flow_netlink.c:2250
Read of size 4 at addr ffff88801ee89970 by task ovs_flow_del_ec/9487
Call Trace:
<TASK>
__ovs_nla_put_key net/openvswitch/flow_netlink.c:1996
ovs_nla_put_key+0x2463/0x2e30 net/openvswitch/flow_netlink.c:2250
ovs_flow_cmd_fill_info+0x420/0x9c0 net/openvswitch/datapath.c:930
ovs_flow_cmd_del+0x53a/0x970 net/openvswitch/datapath.c:1467
...
netlink_rcv_skb+0x156/0x420 net/netlink/af_netlink.c:2556
</TASK>
Allocated by task 9487:
mask_alloc net/openvswitch/flow_table.c:967
flow_mask_insert net/openvswitch/flow_table.c:1012
ovs_flow_tbl_insert+0xea2/0x1a90 net/openvswitch/flow_table.c:1084
ovs_flow_cmd_new+0x7e3/0xd90 net/openvswitch/datapath.c:1086
...
netlink_rcv_skb+0x156/0x420 net/netlink/af_netlink.c:2556
Freed by task 9485:
rcu_free_sheaf+0x1e/0x100 mm/slub.c:5978
rcu_do_batch kernel/rcu/tree.c:2645
rcu_core+0x59c/0x10c0 kernel/rcu/tree.c:2897
handle_softirqs+0x1e4/0x9a0 kernel/softirq.c:622
...
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062
ovs_flow_tbl_remove() must be called after the ovs_flow_cmd_fill_info()
to avoid this race. This also helps with cleaning up the forced cast
and the cosmetic RCU read lock. Before the commit in the Fixes tag the
order did not matter as long as the flow object itself was not freed.
A wider RCU critical section could be another option, but we have a
GFP_KERNEL allocation in the way.
Reported by Trend Micro's Zero Day Initiative as ZDI-CAN-32042.
Fixes: 56c1986 ("openvswitch: Make flow mask removal symmetric.")
Cc: [email protected]
Signed-off-by: Ilya Maximets <[email protected]>
Reviewed-by: Aaron Conole <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
net/openvswitch/flow_netlink.c:1996
net/openvswitch/flow_netlink.c:2250
Diff excerpt:
Not included in this email. See the upstream URL for the full patch.
Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0ba5cbc2f049af94ec94ff6f64958545efc5eaa2
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80994 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80994
The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.
The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.
The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.
Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:
Conservative CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:H
The Best / paranoid CVSS score: 6.5
The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.
CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.
A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.
Conservative ActionableScore: 5
Paranoid ActionableScore: 6
The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.
For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:
ActionableScore below 5 -> MODERATE REGULAR
ActionableScore 5 or more -> MODERATE 7.0
The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.
There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).
KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.
AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0
These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).
Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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