From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99222][MODERATE 7.0] keys: Protect the read method check against type removal Date: Mon, 02 Nov 2026 22:43:35 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99222 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 3 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: e5f830ae6611cddbfc504c43f14155f60b63206a List-Id: CVE: CVE-2026-99222 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: keys: Protect the read method check against type removal Commit: e5f830ae6611cddbfc504c43f14155f60b63206a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e5f830ae6611cddbfc504c43f14155f60b63206a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99222 Analysis date: Mon, 02 Nov 2026 22:43:35 -0400 ActionableScore: 3 ActionableScore lower bound: unknown Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: Concurrent RxRPC key-type removal can make `keyctl_read_key()` read a method field from freed module storage, causing a local race-triggered kernel UAF and possible crash. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99222 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99222 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-2026-99222 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99222 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC) 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-416;CWE-362;*CWE-672;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in keyctl_read_key can occur because the read method is checked outside key sem while key garbage collection can replace the key type and module removal can free the original type storage. A local caller with access to a surviving RxRPC key can repeatedly issue KEYCTL_READ while AF_RXRPC is being unloaded, potentially causing an indirect call through a stale method pointer. For the CVSS the PR:L value is selected because an unprivileged local user can invoke the keyctl read interface for an accessible key, although successful exploitation also depends on concurrent module unload and garbage collection that normally require an external privileged action. The confirmed impact is a kernel crash, while the stale function pointer creates a plausible but unproven control flow and privilege escalation risk that supports the paranoid HHH assessment and manual review. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 3 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were ActionableScore thresholds stage IMPORTANT to MODERATE because the ActionableScore threshold rule was applied. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN5 and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.7 and ActionableScore 2 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) MAYBE LEAK UAF IMPROVEONLY LINUS DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN5 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 3. * Conservative score: 3; no floor or cap applied. * Raw paranoid score: 3. * Paranoid score: 3; no technically supported additional primitive. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown * +2 — Real UAF: `key->type` may reference freed module-resident `key_type` storage when the unlocked method check reads its `read` member. * +1 — Reliable kernel crash/DoS is supported by the supplied triage evidence. * +1 — A low-privilege local caller can repeatedly invoke `KEYCTL_READ` for an accessible key. * -1 — The vulnerable window requires concurrent type unregister, key GC/retyping, and module freeing; the reader does not control the privileged unload operation. * No controlled reclaim, OOB write, stale write, disclosure, or authorization bypass is shown. * No stale indirect call is established: the patch proves a freed `read`-member access, while the actual invocation in `__keyctl_read_key()` occurs under `key->sem` using the protected current type. * No extra availability point is awarded for the same crash, and theoretical CVSS C:H/I:H effects are not scored. 3. Reachability analysis A local user may call `keyctl_read_key()` only for a key passing the existing permission/possession checks. Exploitation additionally depends on AF_RXRPC unloading and associated key GC, ordinarily requiring a separate host-privileged actor. Thus the trigger is compound rather than a fully attacker-controlled unprivileged sequence. The evidence does not establish namespace-scoped control or whether the attacker can induce the module unload, so complete-trigger privilege remains unknown. 4. Primitive and severity reading The primitive is a race-induced UAF read from freed module type storage. It is a shallow stale structured-field access used for a method-presence decision, not a shown stale callback invocation or post-free mutation. The demonstrated effect is crash/DoS; useful control flow, disclosure, or privilege escalation remains speculative. This supports constrained CLASS_B, but not an Important-preserving corruption candidate. Auto-downgrade remains allowed because no material non-crash leverage is shown. 5. One-sentence report phrase Concurrent RxRPC key-type removal can make `keyctl_read_key()` read a method field from freed module storage, causing a local race-triggered kernel UAF and possible crash. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm generated-code behavior and whether any supported configuration lets a low-privilege caller induce or predict AF_RXRPC module removal. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: keys: Protect the read method check against type removal Commit: e5f830ae6611cddbfc504c43f14155f60b63206a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e5f830ae6611cddbfc504c43f14155f60b63206a Commit description: keyctl_read_key() checks key->type->read without holding key->sem. A reference keeps the key alive, but does not pin the module containing its type. A surviving RxRPC key can therefore be read while AF_RXRPC is being unloaded: KEYCTL_READ task Module unload and key GC ---------------- ------------------------ lookup_user_key() permission / possession checks load key->type af_rxrpc_exit() unregister_key_type() GC: down_write(key->sem) GC: retype to key_type_dead GC: up_write(key->sem) unregister_key_type() returns free_module() read saved type's read member The final access can read freed module storage. The read invocation in __keyctl_read_key() is already protected by key->sem, but the earlier method check is outside that critical section. Move the method check into __keyctl_read_key(), after key_validate() and under its existing read hold on key->sem. The check and invocation then use the same protected type for length queries and every read retry. The GC cannot retype the key until the semaphore is released, and type unregistration waits for that GC pass before the module can be freed. Return -EOPNOTSUPP when validation succeeds and the type has no read method. A temporary buffer may now be allocated before this result; allocation and copying to userspace remain outside the semaphore. Assisted-by: LLM Cc: stable@vger.kernel.org # v5.10+ Fixes: d3ec10a ("KEYS: Don't write out to userspace while holding key semaphore") Suggested-by: Jarkko Sakkinen Signed-off-by: Cen Zhang Reviewed-by: Jarkko Sakkinen Reviewed-by: David Howells Link: https://lore.kernel.org/r/pm-key-management-objects-candidate-0010-v7-fc85721ff5cfb9e33ac6@gmail.com Signed-off-by: Jarkko Sakkinen Signed-off-by: Greg Kroah-Hartman Changed files: security/keys/keyctl.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=e5f830ae6611cddbfc504c43f14155f60b63206a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99222 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99222 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:N/I:N/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: unknown 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: 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 alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).