From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99037][MODERATE REGULAR] dm-crypt: reject the lmk IV mode with AEAD ciphers Date: Mon, 26 Oct 2026 23:05:17 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99037 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 0 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 9a0dab8a9d9975dec14a118b55cae2517aea5ca9 List-Id: CVE: CVE-2026-99037 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: dm-crypt: reject the lmk IV mode with AEAD ciphers Commit: 9a0dab8a9d9975dec14a118b55cae2517aea5ca9 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9a0dab8a9d9975dec14a118b55cae2517aea5ca9 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99037 Analysis date: Mon, 26 Oct 2026 23:05:17 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A host administrator can load an invalid AEAD-plus-LMK dm-crypt table that causes an OOB transform-array read and invalid-pointer oops. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99037 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99037 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-99037 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99037 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H';CWE-125;CWE-131;CWE-119;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.7';DESCR 'An incompatible dm-crypt table can combine an AEAD cipher with LMK and make tfms_count equal 64 even though only one AEAD transform was allocated. crypt_setkey then reads beyond the tfms_aead array and passes values from adjacent memory to crypto_aead_setkey which provides a concrete out of bounds access and invalid pointer use primitive. For the CVSS the PR:H value is selected because reliable triggering normally requires root or CAP_SYS_ADMIN access to create and load a device mapper crypt target. The issue is local and not directly network reachable. The demonstrated impact is a kernel oops and denial of service. The paranoid score accounts for possible wider confidentiality and integrity impact from the memory corruption primitive if device mapper administration is delegated across a security boundary although privilege escalation is not established. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 6.7 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold 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_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.3 and ActionableScore 0 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) MAYBE DANGER DISK SIMPLEFIX LINUS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=YES NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 0. * Conservative score: 0; no floor or cap applied. * Raw paranoid score: 0. * Paranoid score: 0; theoretical adjacent-memory effects are not scored. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 weak/indirect corruption candidate: `tfms_count` becomes 64 although only one AEAD transform was allocated, causing `crypt_setkey()` to read beyond `tfms_aead` and pass an invalid value to `crypto_aead_setkey()`. * +1 reliable kernel crash/DoS: the commit specifically reports an oops when the malformed dm-crypt table is loaded. * -2 host-administrator-equivalent privilege: the commit says triggering is root-only, and the supplied call-path summary identifies device-mapper target creation/loading as requiring root or host-level `CAP_SYS_ADMIN`. * No extra availability point: it would duplicate the same oops. * No confirmed OOB write, controlled payload/target, disclosure, UAF, arbitrary write, controlled reclaim, or LPE is shown. * NEW52/B5-R does not apply: there is no retry-accumulated index and no confirmed heap OOB write followed by structured-state consumption. * No score floor applies because this is an invalid OOB read/pointer dereference, not a real UAF or strong corruption primitive. 3. Reachability analysis The complete trigger is a local device-mapper control-plane operation that loads an incompatible dm-crypt table. Evidence positively places it behind effective host-administrator powers. Numeric UID 0 is not strictly required because an appropriately privileged process may use host `CAP_SYS_ADMIN`; however, the supplied source does not establish that an attacker-created user namespace can perform the complete device-mapper operation. There is no remote path, special hardware requirement, retry sequence, or timing race. 4. Primitive and severity reading The exact demonstrated primitive is an array OOB read followed by use of an invalid value as an AEAD transform pointer. This is CLASS_C because the supported outcome is an oops/DoS, with no confirmed write or independently useful corruption primitive. It is neither active structured-state corruption nor stale storage, and no repeated release exists. ImportantCandidate is NO because host-admin-only crash behavior is the supported impact. AutoDowngradeAllowed is YES because no material unknown below-host-admin boundary or non-crash corruption primitive remains. The likely operational severity is ordinary Moderate or lower. 5. One-sentence report phrase A host administrator can load an invalid AEAD-plus-LMK dm-crypt table that causes an OOB transform-array read and invalid-pointer oops. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm the exact capability namespace used by the device-mapper ioctl and verify that `crypto_aead_setkey()` cannot produce a concrete write before faulting. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: dm-crypt: reject the lmk IV mode with AEAD ciphers Commit: 9a0dab8a9d9975dec14a118b55cae2517aea5ca9 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9a0dab8a9d9975dec14a118b55cae2517aea5ca9 Commit description: A "capi:" table line that pairs an AEAD cipher with the lmk IV mode, for example "capi:gcm(aes)-lmk" with the integrity:28:aead option, causes an oops when it is loaded. lmk sets tfms_count to 64, but crypt_alloc_tfms_aead only allocates one transform, so crypt_setkey reads past the end of the tfms_aead array and calls crypto_aead_setkey on the values it finds there. lmk exists for compatibility with Loop-AES, which uses CBC, so refuse it with an AEAD cipher rather than allocate 64 AEAD transforms. The check cannot go in crypt_iv_lmk_ctr with the other lmk checks, because the IV constructor runs after crypt_set_key. Note that this is not a security bug because the memory corruption can only be triggered by root. Fixes: 33d2f09 ("dm crypt: introduce new format of cipher with "capi:" prefix") Cc: stable@vger.kernel.org Signed-off-by: Ben Cressey Assisted-by: LLM Signed-off-by: Mikulas Patocka Signed-off-by: Greg Kroah-Hartman Changed files: drivers/md/dm-crypt.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=9a0dab8a9d9975dec14a118b55cae2517aea5ca9 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99037 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99037 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:H/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 6.7 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: 0 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 alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).