* [CVE-2026-80924][MODERATE REGULAR] crypto: krb5 - use kfree_sensitive() for derived key buffers
@ 2026-09-09 17:01 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-09 17:01 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-80924
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: crypto: krb5 - use kfree_sensitive() for derived key buffers
Commit: 731a5b6fb4c1705f9405d9029dd64ea81e336207
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=731a5b6fb4c1705f9405d9029dd64ea81e336207
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80924
Analysis date: Wed, 09 Sep 2026 13:01:09 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80924 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80924
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 REGULAR
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-2026-80924 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-80924 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:N/A:N';CWE-226;CWE-312;CWE-212;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '4.7';DESCR 'Derived Kerberos key material in crypto_krb5_prepare_encryption() and crypto_krb5_prepare_checksum() was released with kfree(), so sensitive key bytes could remain in a freed slab object after the temporary buffer was deallocated. This is primarily an information exposure risk rather than memory corruption, because the patch shows stale secret data in kernel heap memory but does not show an overwrite, UAF access, or direct crash primitive. For the CVSS the PR:L is used for the paranoid score because practical exploitation would normally require a local process or service context that can trigger Kerberos crypto usage and also obtain freed kernel memory through another exposure path. The issue is not directly network reachable by itself, although Kerberos use may be part of network filesystems or authentication flows. Impact is confidentiality loss only, with higher concern because the leaked material is cryptographic key data.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) YES UAF LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 YES NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline / manual review recommended**::
No floor or cap was applied.
2. Signal breakdown
Conservative positive signals:
* +1. Concrete sensitive-data remanence. The patch directly shows derived Kerberos key buffers being freed with `kfree()` instead of being wiped before free.
* +1. High-value secret material. The retained data is freshly derived Kerberos key material, so the affected bytes are security-sensitive even though no direct disclosure path is shown.
Paranoid additional signal:
* +1. Deployment-dependent confidentiality concern. If another kernel heap disclosure or slab reuse exposure exists in the same environment, residual Kerberos key bytes could become more security-significant. This is not treated as a direct disclosure primitive.
Non-awarded signals:
* Controlled reclaim not demonstrated.
* Arbitrary read or write not demonstrated.
* Real UAF not established.
* Kernel crash or availability impact not demonstrated.
* Remote reachability not established by this patch alone.
* Confidentiality impact is not awarded as a concrete primitive because the patch does not show a read-back path from freed slab memory to userspace, network, device output, or another protected observer.
* Integrity impact not awarded.
* Privilege escalation not awarded.
* No concrete repeated release/refcount operation exists.
* No security-boundary authorization bypass exists.
3. Reachability analysis
The affected functions are kernel crypto helpers for Kerberos encryption and checksum setup. The patch does not show a direct userspace syscall or network packet path that exposes the freed slab contents.
An attacker may be able to influence whether Kerberos crypto is used indirectly through subsystems such as authenticated network filesystems or RPC security, but the complete trigger and disclosure chain is not established in the supplied context.
Host-admin-equivalent privilege is not positively established, but below-host-admin reachability is also not positively established. Therefore HostAdminRequired is UNKNOWN.
Namespace-scoped privilege is not established. There is no evidence that the complete operation is available inside attacker-created namespaces.
No special hardware is required. No race is involved. No prior privileged setup can be concluded from the patch alone, although practical exposure depends on whether the affected Kerberos crypto path is used by the target system.
4. Primitive and severity interpretation
The exact primitive is failure to erase sensitive key material before freeing a kernel heap buffer.
This is not memory corruption. It is not a UAF. It is not a double free. It is not an OOB access. It is not a crash bug.
The demonstrated consequence is residual Kerberos key material remaining in freed slab memory after `crypto_krb5_prepare_encryption()` or `crypto_krb5_prepare_checksum()` completes or fails.
The speculative consequence is information exposure if some separate mechanism later discloses or reuses the freed slab contents in an observable way. That separate disclosure mechanism is not established here.
PrimitiveClass is NONE because the patch establishes sensitive-data remanence, but not a corruption, lifetime, ownership, authorization, or direct disclosure primitive.
ImportantCandidate is NO because there is no demonstrated exploit chain, no direct read primitive, no memory corruption, no privilege escalation path, and no boundary bypass.
AutoDowngradeAllowed is YES because this is a low-to-borderline issue unless the evaluated product has an additional credible kernel heap disclosure path or a particularly sensitive Kerberos deployment dependency.
Likely operational severity is ordinary Moderate or Low-like, with manual review recommended due to the cryptographic nature of the residual secret.
5. One-sentence report phrase
Derived Kerberos key buffers were freed without being wiped, leaving sensitive key material in freed slab memory and creating a potential confidentiality risk if another path can expose reused kernel heap contents.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
The issue does not establish direct disclosure or corruption, but the affected data is cryptographic key material and deployment-specific Kerberos usage may make the residual-memory risk more important.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: crypto: krb5 - use kfree_sensitive() for derived key buffers
Commit: 731a5b6fb4c1705f9405d9029dd64ea81e336207
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=731a5b6fb4c1705f9405d9029dd64ea81e336207
Commit description:
crypto_krb5_prepare_encryption() and crypto_krb5_prepare_checksum()
free the buffer holding the freshly derived keys with plain kfree(),
leaving the key material behind in the freed slab object.
Fixes: 3936f02 ("crypto/krb5: Implement Kerberos crypto core")
Cc: [email protected]
Signed-off-by: Jan Sebastian Götte <[email protected]>
Signed-off-by: Herbert Xu <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
crypto/krb5/krb5_api.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=731a5b6fb4c1705f9405d9029dd64ea81e336207
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80924 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80924
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:N/A:N
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
The Best / paranoid CVSS score: 4.7
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: 2
Paranoid ActionableScore: 3
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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR
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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