* [CVE-2026-98240][LOW] net: ip_tunnel: initialize options_len before referencing options
@ 2026-10-09 16:53 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-09 16:53 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98240
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net: ip_tunnel: initialize options_len before referencing options
Commit: 9907325257b4b382f26aafd5d9a8d47915907dd5
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9907325257b4b382f26aafd5d9a8d47915907dd5
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98240
Analysis date: Fri, 09 Oct 2026 12:53:39 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98240 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98240
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: LOW
Manual review required: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-98240 LOW https://www.kernelcve.org/list/?q=CVE-2026-98240 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=LOW RESULT=DIFF TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (independent Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-665;*CWE-457;CWE-754;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'The IP tunnel option parser can reach a fortified memcpy before info options_len is initialized even though storage for the tunnel options has already been allocated. On kernels built with GCC 15 or later and CONFIG_FORTIFY_SOURCE, the counted flexible array is therefore interpreted as having a zero sized destination and copying a Geneve option triggers a kernel BUG and panic. The demonstrated primitive is a deterministic local denial of service rather than an actual out of bounds write, UAF, information leak, or privilege escalation. For the CVSS the PR:L value is used for the paranoid score because a local user may be able to obtain CAP_NET_ADMIN in an available user and network namespace and configure the affected route while the resulting panic affects the shared host kernel. The base score uses PR:H because route and tunnel configuration normally requires administrative network privileges. The issue is not directly network reachable because received packets do not create the malformed state. It must be triggered through a local netlink control plane operation. Impact is limited to availability and requires GCC 15 or later with CONFIG_FORTIFY_SOURCE for the demonstrated panic.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE REMOTE OOB DANGER INIT NETWORK IPV6 DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 2
* Paranoid score: 2
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
Positive signals:
* +1 Reliable kernel crash. The supplied reproducer triggers a FORTIFY kernel BUG when `memcpy()` observes a four-byte copy into a destination whose `__counted_by` size is still zero.
* +1 Memory layout invariant restoration. The allocation includes `opt_len` bytes, but the flexible-array count used by fortified object-size analysis is not initialized until after parsing. The fix makes allocation size, flexible-array metadata, and copy operation consistent.
Negative signals:
* No negative privilege penalty. Host-admin-equivalent privilege is not positively established for the complete trigger, but below-host-admin namespace reachability is also not fully established.
* No race or timing penalty. The failure is deterministic under the affected build conditions.
* No rarity penalty. GCC 15 or later with `CONFIG_FORTIFY_SOURCE` is a build prerequisite, but the evidence does not establish a genuinely rare and inaccessible subsystem.
Important non-awarded signals:
* No actual heap OOB write is established. Storage for the options was allocated using `opt_len`. The zero size is fortified object-size metadata derived from the late `options_len` initialization.
* The NEW52 B5-R profile does not apply. There is no retry-accumulated index, no offset growth across re-entry, and no corrupted descriptor or structured state later consumed by the kernel.
* No UAF, controlled reclaim, arbitrary write, disclosure, authorization bypass, or privilege-escalation primitive is demonstrated.
* No remote-reachability point. The trigger is a local rtnetlink control-plane operation, not incoming packet traffic.
* No extra Availability point. The same kernel BUG is already counted once as reliable crash or strong DoS.
* No C or I signal. The fortified copy aborts before a demonstrated corruption primitive is produced.
3. Reachability analysis
The trigger configures an IP route with Geneve lightweight-tunnel options through rtnetlink and therefore requires `CAP_NET_ADMIN` for the relevant network namespace.
The supplied reproducer does not establish whether the operation runs in the initial network namespace or in an attacker-created user and network namespace. On systems allowing unprivileged user-namespace creation, a local user may be able to obtain namespace-scoped `CAP_NET_ADMIN`, create a dummy device, and configure the route. The supplied evidence does not prove that the complete sequence is available under the evaluated product configuration. Therefore:
* Host-admin requirement is unresolved.
* Complete namespace-scoped reachability is unresolved.
* No ordinary-unprivileged trigger bonus is awarded.
* No host-admin penalty is applied.
* No prior privileged setup is established beyond the affected kernel build.
* No special hardware is required.
* The demonstrated trigger is deterministic rather than race-dependent.
* Incoming network traffic cannot directly reach the vulnerable operation.
4. Primitive and severity interpretation
The exact primitive is an initialization-order mismatch involving the `options_len` field that serves as the `__counted_by` value for the flexible `options` array. Although the allocation already contains space for `opt_len` bytes, fortified `memcpy()` observes a zero-sized destination because the count field has not yet been initialized.
This is a CLASS_C crash or invalid-state condition. It is not a real OOB corruption primitive based on the supplied allocation and call-path evidence. The demonstrated consequence is a local kernel panic on affected fortified builds. Theoretical memory corruption, confidentiality impact, integrity impact, and privilege escalation are unsupported.
ImportantCandidate is NO because neither B5-R nor another Important-preserving primitive is established. AutoDowngradeAllowed is YES because the behavior is a deterministic configuration-dependent DoS with no unresolved lifetime, ownership, authorization, or corruption primitive.
Likely operational severity is Low-like to ordinary Moderate depending on whether namespace-scoped route configuration is available to untrusted local users.
5. One-sentence report phrase
Late initialization of the IP tunnel flexible-array count causes fortified memcpy to report a zero-sized destination and panic the kernel during privileged or potentially namespace-scoped route configuration, without establishing an actual out-of-bounds write.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch establishes a FORTIFY-triggered local DoS rather than NEW52 B5-R retry-accumulated corruption, and no Important-preserving primitive remains unresolved.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: net: ip_tunnel: initialize options_len before referencing options
Commit: 9907325257b4b382f26aafd5d9a8d47915907dd5
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9907325257b4b382f26aafd5d9a8d47915907dd5
Commit description:
The following command triggers a kernel panic:
ip link add d0 type dummy; ip link set d0 up
ip route add 10.30.0.0/16 \
encap ip id 300 geneve_opts 4660:66:11223344 dev d0
memcpy: detected buffer overflow: 4 byte write of buffer size 0
kernel BUG at lib/string_helpers.c:1044!
...
ip_tun_parse_opts.part.0.cold+0x10/0x10
ip_tun_build_state+0x116/0x2a0
On kernels built with GCC 15+ and `CONFIG_FORTIFY_SOURCE`, the fortified
`memcpy()` got 0 sized destination with request of 4 bytes length:
static int ip_tun_parse_opts_geneve(...)
{
...
attr = tb[LWTUNNEL_IP_OPT_GENEVE_DATA];
data_len = nla_len(attr); /* == 4 */
struct geneve_opt *opt = ip_tunnel_info_opts(info) + opts_len;
memcpy(opt->opt_data, nla_data(attr), data_len);
/* ^^^^^^^^^^^^^ 0 since options_len is assigned afterwards */
Fixed by initializing the counter before the options are referenced.
Matching what `tunnel_key_opts_set()` already does.
Fixes: bb5e62f ("net: Add options as a flexible array to struct ip_tunnel_info")
Cc: [email protected]
Signed-off-by: Gris Ge <[email protected]>
Reviewed-by: Hangbin Liu <[email protected]>
Reviewed-by: Gustavo A. R. Silva <[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:
lib/string_helpers.c
net/ipv4/ip_tunnel_core.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=9907325257b4b382f26aafd5d9a8d47915907dd5
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98240 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98240
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:L/PR:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 5.5
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: unknown
Paranoid ActionableScore: 2
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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW
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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