From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74592][MODERATE 7.0] ima: Instantiate file_truncate and path_truncate hooks Date: Sat, 22 Aug 2026 15:25:00 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74592 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 5f46705d96eb60587aa7035acfcbec977e08d620 List-Id: CVE: CVE-2026-74592 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: ima: Instantiate file_truncate and path_truncate hooks Commit: 5f46705d96eb60587aa7035acfcbec977e08d620 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5f46705d96eb60587aa7035acfcbec977e08d620 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74592 Analysis date: Sat, 22 Aug 2026 15:25:00 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: NO Summary: IMA truncate handling failed to invalidate cached action flags, so a locally triggered truncate could leave stale measurement or appraisal state and weaken IMA based integrity enforcement on the next file access. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74592 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74592 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-74592 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW 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:H/A:N';CWE-693;CWE-345;CWE-354;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N';BEST CVSS score: '5.5';DESCR 'IMA truncate handling could leave cached IMA action flags valid after a regular file was truncated, so later access might rely on stale measurement or appraisal state even though file contents changed. This can weaken IMA based integrity enforcement because the file may not be re measured, re audited, or re appraised on the next access according to policy. For the CVSS the PR:L value is used because a local user or process must be able to request truncate or ftruncate on the affected file, but full administrator privileges are not inherently required in all deployments. The issue is not directly network reachable and does not indicate memory corruption. Impact is primarily an integrity policy bypass, with higher concern on systems where IMA appraisal is enforced for trusted executables or critical files.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum:: (with actual score 4) YES READ LOCK INIT LINUS INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum::** ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1. A local process that can truncate or ftruncate a regular file can reach the affected hooks. * Security-boundary or policy-bypass concern: +2. IMA appraisal and measurement are security policy mechanisms, and stale IMA_DONE_MASK state may prevent re-measurement or re-appraisal after file content changes. * Integrity impact plausible: +1. The primary risk is stale integrity state after truncation, potentially allowing modified content to be treated as already processed. * Rare or configuration-dependent exposure: -1. Meaningful impact depends on IMA policy being enabled, and especially on appraisal or measurement policy being relevant to the target file. Paranoid additions: * Practical exploit chain strongly implied: +1. The commit directly describes the chain truncate requested -> IMA action cache not reset -> next access may skip re-collection, re-measurement, re-audit, or re-appraisal. * Security-enforcement deployment sensitivity: +1. On systems using IMA appraisal in enforce mode for trusted executables or critical files, stale appraisal state can be more operationally significant than a generic correctness bug. Call-site confidence: high. The patch directly adds file_truncate and path_truncate LSM hooks and shows the exact IMA cache state being invalidated. ## 3. Reachability analysis The bug is locally reachable through truncate paths for regular files. Full root privileges are not inherently required, because a normal local user may be able to truncate files they own or files writable through delegated permissions. Namespaces and containers can matter if IMA policy applies across the host or to shared files, but practical impact depends heavily on how IMA appraisal and measurement policies are configured. The path is not network reachable by itself. It is not a memory corruption issue, and there is no UAF, OOB access, arbitrary write, or kernel crash primitive shown by the patch. ## 4. Severity interpretation This behaves more like an actionable Moderate integrity policy bypass than an ordinary low-risk cleanup. The realistic impact is stale IMA measurement or appraisal state after file truncation, with integrity consequences dependent on deployment policy. The theoretical worst case is stronger on systems where IMA appraisal is used as an enforced trust boundary for executables or critical files. There is no realistic evidence of privilege escalation through memory corruption, and no confidentiality or availability impact is directly supported. ## 5. One-sentence report phrase IMA truncate handling failed to invalidate cached action flags, so a locally triggered truncate could leave stale measurement or appraisal state and weaken IMA based integrity enforcement on the next file access. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Manual review is recommended because the impact depends on IMA policy, appraisal enforcement mode, and whether affected files are part of a trusted execution or integrity boundary. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ima: Instantiate file_truncate and path_truncate hooks Commit: 5f46705d96eb60587aa7035acfcbec977e08d620 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5f46705d96eb60587aa7035acfcbec977e08d620 Commit description: Instantiate the file_truncate and path_truncate LSM hooks to reset the action cache flags (IMA_DONE_MASK) as soon as truncation is requested, so the file, based on policy, is re-collected, re-measured, re-audited, and re-appraised on next access. Tested-by: Frederick Lawler Cc: stable@vger.kernel.org Signed-off-by: Mimi Zohar Signed-off-by: Greg Kroah-Hartman Changed files: security/integrity/ima/ima_main.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=5f46705d96eb60587aa7035acfcbec977e08d620 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74592 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74592 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:L/UI:N/S:U/C:N/I:L/A:N The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N 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: 3 Paranoid ActionableScore: 5 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 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).