From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-89989][MODERATE REGULAR] ima: Check for ERR_PTR from dentry_path() in validate_hash_algo() Date: Wed, 16 Sep 2026 11:24:46 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-89989 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: 2 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: d6fade89903c8fd0af6c956242aec8b927040e02 List-Id: CVE: CVE-2026-89989 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: ima: Check for ERR_PTR from dentry_path() in validate_hash_algo() Commit: d6fade89903c8fd0af6c956242aec8b927040e02 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d6fade89903c8fd0af6c956242aec8b927040e02 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89989 Analysis date: Wed, 16 Sep 2026 11:24:46 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: IMA `validate_hash_algo()` failed to check `ERR_PTR` from `dentry_path()`, allowing a local IMA setxattr validation path with an overlong pathname to dereference an error pointer in `strlen()` and crash the kernel. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89989 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89989 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-2026-89989 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89989 CHECK WITH IMPACT FROM ORIG NN MODERATE 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-252;**CWE-476;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 'IMA validate_hash_algo passed the return value of dentry_path directly into integrity_audit_msg without checking for ERR_PTR. If the pathname is too long, dentry_path can return ERR_PTR(-ENAMETOOLONG), and the audit path can treat it as a valid string pointer and fault in strlen, causing a local kernel crash or oops. For the CVSS the PR:L is used in the paranoid score because some deployments may delegate the relevant xattr or security policy operations to a less privileged local process, although PR:H is more typical on standard systems. The issue is not network reachable and requires local interaction with the IMA setxattr validation path. Impact is denial of service only. There is no supported UAF, OOB write, arbitrary write, information leak, or privilege escalation primitive in this patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES DANGER SIMPLEFIX LINUS SYZBOT DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES ## 1. ActionableScore * Raw conservative score: 2 * Conservative score: 2 * Raw paranoid score: 2 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate**:: No floor or cap was applied. ## 2. Signal breakdown Positive signals: * +1 Weak or indirect corruption candidate: `dentry_path()` can return `ERR_PTR(-ENAMETOOLONG)`, and this error pointer is incorrectly treated as a valid string pointer. * +1 Reliable kernel crash / strong DoS: the bad pointer reaches `strlen()` through the audit path and causes a kernel page fault or oops. Negative or non-awarded signals: * Real UAF: not awarded. No object lifetime violation, stale object reuse, or post-free access is established. * Concrete repeated release/refcount: not awarded. There is no first release, surviving dangling reference, or second lifetime mutation. * Controlled reclaim: not demonstrated. * Arbitrary write or directed kernel write: not demonstrated. * Confidentiality and integrity: not awarded. The primitive is an invalid error-pointer dereference, not an information leak or write primitive. * Remote reachability: not established. The path is local through IMA `setxattr` validation. * Security-boundary bypass: not established. The patch does not show an ALLOW-vs-DENY authorization failure. * Extra availability point: not awarded because the same crash is already counted once. * Paranoid escalation: withheld because there is no UAF, OOB write, arbitrary write, authorization bypass, or other stronger primitive. ## 3. Reachability analysis The vulnerable path is reached through `ima_inode_setxattr()` and `validate_hash_algo()` when IMA validates a hash algorithm and emits an audit message. The trigger requires a pathname long enough for `dentry_path()` to return `ERR_PTR(-ENAMETOOLONG)`. The exact privilege boundary depends on IMA policy and xattr permissions in the evaluated system. Standard deployments commonly restrict relevant IMA or security xattr operations to administrative capability, but the supplied evidence does not fully prove a host-admin-equivalent requirement for every configuration. Therefore `HostAdminRequired=UNKNOWN`. No evidence shows that the complete trigger chain is namespace-scoped. There is no network trigger. No special hardware is required. No race or narrow timing window is involved. ## 4. Primitive and severity interpretation The exact primitive is an unchecked `ERR_PTR` value being passed as a pathname string into `integrity_audit_msg()`, where it is later consumed by `strlen()`. This is an invalid pointer dereference, not a heap UAF, not an RCU lifetime bug, and not a repeated refcount/lifetime mutation. This is Class C behavior: demonstrated consequence is crash or oops only. There is no established exploitation leverage beyond denial of service. ImportantCandidate is NO because no meaningful memory corruption, security-boundary bypass, privileged resource access, or LPE path is supported by the patch or supplied context. AutoDowngradeAllowed is YES because the issue is crash-only Class C with no unresolved concrete corruption primitive. ## 5. One-sentence report phrase IMA `validate_hash_algo()` failed to check `ERR_PTR` from `dentry_path()`, allowing a local IMA setxattr validation path with an overlong pathname to dereference an error pointer in `strlen()` and crash the kernel. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: manual review is useful to confirm product-specific reachability, IMA policy requirements, and xattr privilege boundaries, but the demonstrated bug class remains DoS-only and does not require Important-level treatment from the supplied evidence. ## 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ima: Check for ERR_PTR from dentry_path() in validate_hash_algo() Commit: d6fade89903c8fd0af6c956242aec8b927040e02 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d6fade89903c8fd0af6c956242aec8b927040e02 Commit description: dentry_path() returns ERR_PTR(-ENAMETOOLONG) when the path exceeds the buffer. validate_hash_algo() passes the result straight to integrity_audit_msg() without checking. ERR_PTR is not NULL, so integrity_audit_message() sees a valid pointer and calls strlen() on it, which faults: BUG: unable to handle page fault for address: ffffffffffffffdc RIP: 0010:strlen+0x30/0xa0 Call Trace: audit_log_untrustedstring+0x19/0x30 integrity_audit_message+0x366/0x4f0 ima_inode_setxattr+0x512/0x5f0 Check for IS_ERR() and use NULL instead, which makes the audit message skip the name= field instead of crashing. Fixes: 4f2946a ("IMA: introduce a new policy option func=SETXATTR_CHECK") Cc: stable@vger.kernel.org Reported-by: syzbot+5ebeb3089ea6439c37be@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/6a8f89e5.1d9ded08.62e62.00bf.GAE@google.com/ Signed-off-by: Bradley Morgan Signed-off-by: Mimi Zohar Signed-off-by: Greg Kroah-Hartman Changed files: security/integrity/ima/ima_appraise.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=d6fade89903c8fd0af6c956242aec8b927040e02 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89989 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89989 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: 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).