* [CVE-2026-80852][IMPORTANT] tls: device: fix out-of-bounds write in tls_append_frag()
@ 2026-09-04 17:38 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-04 17:38 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-80852
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: tls: device: fix out-of-bounds write in tls_append_frag()
Commit: 03ced5da6120965d80ed56dbb7d78fa5c9128906
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=03ced5da6120965d80ed56dbb7d78fa5c9128906
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80852
Analysis date: Fri, 04 Sep 2026 13:38:04 -0400
ActionableScore: 7
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES
Summary:
A local out-of-bounds write in the kTLS device offload transmit path can be triggered through fragmented MSG_MORE splice traffic, leading to kernel memory corruption and at least a reliable crash, with credible privilege-escalation concern because the observed corruption reaches workqueue control data.
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ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80852 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80852
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: IMPORTANT
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-2026-80852 IMPORTANT https://www.kernelcve.org/list/?q=CVE-2026-80852 CHECK WITH IMPACT FROM ORIG NN LOW 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:H/A:H';*CWE-787;CWE-122;CWE-119;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'An out of bounds write in the kTLS device offload transmit path can occur when tls_push_data keeps a record open with MSG_MORE even after the record is near the maximum fragment count. Repeated splice operations with SPLICE_F_MORE can add non coalescing pipe pages until record num_frags exceeds MAX_SKB_FRAGS, after which tls_append_frag and later tls_push_record access frags and sg_tx_data past their fixed arrays. This is local kernel memory corruption and the observed failure includes writes reaching destruct_work followed by a workqueue attempting to execute a corrupted pointer. For the CVSS the PR:L is used because a local user or process with access to a socket using kTLS device offload may be able to drive the transmit path, while direct network only triggering is not supported by the patch context. Impact is at least local denial of service via kernel crash and in the paranoid case may include confidentiality and integrity impact due to an out of bounds write and possible control flow corruption. Practical exposure depends on TLS device offload support, for example a capable NIC or netdevsim style test setup, and TLS_TX_ZEROCOPY_RO usage.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7) YES REMOTE WRITE KASAN OOB SKB HARDWARE SYZBOT KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS NO NO checked
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ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=7
ActionableScoreLower=6
## 1. ActionableScore
* Conservative score: 6
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::
## 2. Signal breakdown
Conservative signals:
* Local unprivileged trigger: +1. The path is driven by local socket send/splice operations against kTLS device offload.
* Memory corruption, strong corruption primitive: +2. The commit explicitly describes slab out-of-bounds write in `tls_append_frag()` and OOB array accesses in `tls_push_record()`.
* Memory layout invariant restoration: +1. The bug is a mismatch between record byte accounting and fragment-count accounting, allowing `num_frags` to exceed `MAX_SKB_FRAGS`.
* Reliable kernel crash / strong DoS: +1. KASAN, UBSAN, Oops, and workqueue execution through corrupted state are shown.
* Local high-control kernel data-plane API refinement: +1. `splice(SPLICE_F_MORE)`, pipe pages, socket send paths, and kTLS offload allow fine-grained shaping of fragments.
* Rare/configuration-dependent exposure: -1. `tls_device.c` is reachable only with TLS device offload support, such as capable NIC hardware or netdevsim-style emulation.
* Weak-to-strong LPE concern in conservative scoring: +1. The observed overwrite reaches `destruct_work`, but a reliable privilege-escalation primitive is not demonstrated.
Paranoid delta:
* Strong LPE plausibility: upgrade +1. The OOB write corrupts adjacent workqueue-related control data and the workqueue later attempts to execute a corrupted pointer, which is a credible control-flow-corruption concern requiring manual review.
## 3. Reachability analysis
The bug is not realistically network-triggerable by a remote peer sending packets. It is in the local transmit path for kTLS device offload and is reached through local socket operations such as `sendmsg()` and `splice()`. A local user or process with access to a socket using kTLS device offload may be able to trigger it, so PR:L is the practical privilege assumption rather than PR:N.
The main limiting condition is deployment exposure. Systems need NIC TLS offload support or an equivalent emulated setup, and the vulnerable path depends on `TLS_TX_ZEROCOPY_RO` style behavior with fragmented splice input. This is not a universal default path, but it is security-relevant on affected hosts because the primitive is a kernel OOB write rather than a mere warning or validation failure.
## 4. Severity interpretation
This should not be treated as ordinary Moderate or auto-closed. The realistic demonstrated impact is local kernel crash / DoS, but the primitive is stronger than DoS-only because the write goes past fixed arrays and reaches nearby workqueue state. The evidence does not prove a working LPE exploit, but it is enough for an Important-candidate manual review path due to OOB write plus possible callback/control-flow corruption.
## 5. One-sentence report phrase
A local out-of-bounds write in the kTLS device offload transmit path can be triggered through fragmented MSG_MORE splice traffic, leading to kernel memory corruption and at least a reliable crash, with credible privilege-escalation concern because the observed corruption reaches workqueue control data.
## 6. Manual review recommendation
MANUAL CHECK REQUIRED
Reason: this is a kernel OOB write with demonstrated corruption of adjacent workqueue-related state and a later attempted indirect execution path, so it should be reviewed manually even though practical exposure depends on TLS device offload availability.
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: tls: device: fix out-of-bounds write in tls_append_frag()
Commit: 03ced5da6120965d80ed56dbb7d78fa5c9128906
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=03ced5da6120965d80ed56dbb7d78fa5c9128906
Commit description:
Found with syzkaller and a local syzbot instance running on top of a
netdevsim TLS offload emulation; tls_device.c is otherwise only reachable
on a machine with a NIC that implements the offload.
tls_push_data() only checks whether the open record still has room for
another frag at the bottom of its loop, and the MSG_MORE early break
skips that check. The record survives to the next syscall with the frag
count it already had, and tls_append_frag() does not check either, so
with TLS_TX_ZEROCOPY_RO every splice(SPLICE_F_MORE) of a byte or two adds
a non-coalescing pipe page and num_frags walks off the end of
tls_record_info.frags[MAX_SKB_FRAGS]. Once the record is pushed,
tls_push_record() runs the same index over sg_tx_data[MAX_SKB_FRAGS] and
the sg_set_page() writes land on the destruct_work that follows it, which
the workqueue then calls.
The byte limit is fine because copy drops to 0 and the loop falls through
to the same check; the frag count has no such feedback.
Push the record rather than keep a full one open, which is what a plain
TCP socket does - tcp_sendmsg_locked() uses tcp_mark_push() and
new_segment in both the copy and the MSG_SPLICE_PAGES paths, and tls_sw
already sets full_record when the sk_msg ring fills up, MSG_MORE or not.
BUG: KASAN: slab-out-of-bounds in tls_append_frag ( net/tls/tls_device.c:269)
Write of size 8 at addr ffff8881104d1530 by task tls_oob/450
CPU: 2 UID: 0 PID: 450 Comm: tls_oob Not tainted 7.2.0-rc7+ #329 PREEMPT
Call Trace:
<TASK>
dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
print_report (mm/kasan/report.c:378 mm/kasan/report.c:482)
kasan_report (mm/kasan/report.c:595)
tls_append_frag (net/tls/tls_device.c:269)
tls_push_data (net/tls/tls_device.c:518)
tls_device_sendmsg (net/tls/tls_device.c:583)
inet_sendmsg (net/ipv4/af_inet.c:865)
sock_sendmsg (net/socket.c:775 net/socket.c:790 net/socket.c:813)
splice_to_socket (fs/splice.c:884)
do_splice (fs/splice.c:936 fs/splice.c:1349)
__do_splice (fs/splice.c:1431)
__x64_sys_splice (fs/splice.c:1634 fs/splice.c:1616)
do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
</TASK>
and, once the record is pushed:
UBSAN: array-index-out-of-bounds in net/tls/tls_device.c:300:24
index 18 is out of range for type 'skb_frag_t [17]'
UBSAN: array-index-out-of-bounds in net/tls/tls_device.c:301:41
index 18 is out of range for type 'scatterlist [17]'
UBSAN: array-index-out-of-bounds in net/tls/tls_device.c:302:39
index 18 is out of range for type 'scatterlist [17]'
UBSAN: array-index-out-of-bounds in net/tls/tls_device.c:307:38
index 26 is out of range for type 'scatterlist [17]'
kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
BUG: unable to handle page fault for address: ffffea000411a680
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0011) - permissions violation
Oops: Oops: 0011 [#1] SMP KASAN PTI
Workqueue: ktls_device_destruct 0xffffea000411a680
RIP: 0010:0xffffea000411a680
Call Trace:
<TASK>
worker_thread (kernel/workqueue.c:3405 kernel/workqueue.c:3486)
kthread (kernel/kthread.c:436)
ret_from_fork (arch/x86/kernel/process.c:158)
ret_from_fork_asm (arch/x86/entry/entry_64.S:245)
</TASK>
Fixes: e8f6979 ("net/tls: Add generic NIC offload infrastructure")
Cc: [email protected]
Signed-off-by: Jiayuan Chen <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
net/tls/tls_device.c
lib/dump_stack.c
mm/kasan/report.c
net/ipv4/af_inet.c
net/socket.c
fs/splice.c
arch/x86/entry/syscall_64.c
arch/x86/entry/entry_64.S
kernel/workqueue.c
kernel/kthread.c
arch/x86/kernel/process.c
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=03ced5da6120965d80ed56dbb7d78fa5c9128906
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80852 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80852
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:L/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7
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: 6
Paranoid ActionableScore: 7
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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT
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
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