From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72316][LOW] dm era: fix NULL pointer dereference in metadata_open() [ Upstream Date: Sat, 15 Aug 2026 04:09:59 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72316 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: 0 X-AL-KERNEL-Commit: a705e056c2f3dd067fb2ff414f0537530baa090b List-Id: CVE: CVE-2026-72316 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: YES Patch: dm era: fix NULL pointer dereference in metadata_open() [ Upstream Commit: a705e056c2f3dd067fb2ff414f0537530baa090b Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a705e056c2f3dd067fb2ff414f0537530baa090b Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72316 Analysis date: Sat, 15 Aug 2026 04:09:59 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like, auto-close candidate Manual review required: NO Summary: A dm-era error handling bug can treat a failed metadata allocation as a valid pointer, causing a privileged local NULL pointer dereference and kernel crash during metadata access. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72316 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72316 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: LOW 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-2026-72316 LOW CHECK WITH IMPACT FROM ORIG NN NONE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-252;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'dm era metadata_open can return NULL when kzalloc_obj fails, while era_ctr only checks IS_ERR and can treat NULL as a valid metadata pointer. A local administrator or process with device mapper configuration privileges can reach this path while creating a dm era target under memory pressure, causing a later NULL pointer dereference when metadata is accessed. For the CVSS the PR:L is used for the paranoid score because some environments delegate storage administration to service accounts or container root like contexts, although typical host configuration requires CAP_SYS_ADMIN. The issue is not network reachable. Impact is denial of service via kernel crash only, with no evidence of an information leak or write primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like, auto-close candidate (with actual score 1) YES NULLPTR DISK NOMEMCHK SIMPLEFIX IMPROVEONLY LINUS KPANIC NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like, auto-close candidate**:: ## 2. Signal breakdown * +1 Reliable kernel crash / strong DoS: allocation failure can lead to a NULL metadata pointer being stored and later dereferenced. * +1 Important filesystem/storage path: this is in device-mapper dm-era metadata setup. * -2 Requires admin/root/CAP_SYS_ADMIN in typical deployments: creating/configuring dm targets normally requires privileged device-mapper access. * -1 Hard or special condition: practical triggering depends on allocation failure during target creation, i.e. memory pressure or fault injection. * No generic memory corruption: this is a NULL pointer dereference, not UAF, double-free, OOB write, refcount corruption, or type confusion. * No LPE signal: no attacker-controlled reclaim, overwrite target, stale callback, refcount takeover, or write primitive is shown. * No confidentiality or integrity signal: impact is crash only. ## 3. Reachability analysis The bug is reachable during dm-era target creation when `metadata_open()` fails allocation and returns NULL instead of `ERR_PTR(-ENOMEM)`. In normal deployments, device-mapper target setup requires root or CAP_SYS_ADMIN, so this is not a local unprivileged interface. A paranoid interpretation can consider delegated storage-management contexts, service accounts, or container-root-like environments, but even then the trigger still depends on allocation failure and only leads to NULL dereference DoS. The path is not network reachable and dm-era is not a broad default attack surface. Call-site confidence: high, because the commit explicitly describes the caller `era_ctr()` and the `IS_ERR()` versus NULL handling mismatch. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like kernel DoS issue, not an Important-class vulnerability. The theoretical failure is reliable once the bad allocation state is reached, but realistic exploitation requires privileged device-mapper configuration plus memory-allocation failure timing. There is no supported evidence of memory corruption beyond NULL dereference, privilege escalation, information disclosure, or integrity impact. ## 5. One-sentence report phrase A dm-era error handling bug can treat a failed metadata allocation as a valid pointer, causing a privileged local NULL pointer dereference and kernel crash during metadata access. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED. This can be auto-closed for urgent triage because it is a privileged local NULL pointer dereference with allocation-failure dependency and no demonstrated memory corruption or privilege-escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: dm era: fix NULL pointer dereference in metadata_open() [ Upstream Commit: a705e056c2f3dd067fb2ff414f0537530baa090b Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a705e056c2f3dd067fb2ff414f0537530baa090b Changed files: drivers/md/dm-era-target.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=a705e056c2f3dd067fb2ff414f0537530baa090b ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72316 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72316 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:H/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:N/I:N/A:H 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: 0 Paranoid ActionableScore: 1 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: LOW KPANIC detected for this report: YES Published priority for this report (same as in Subject): LOW 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).