From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72276][LOW] fbdev: metronomefb: fix potential memory leak in metronomefb_probe() Date: Sat, 15 Aug 2026 16:48:56 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72276 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 0 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 77e26383083c59a67244fcf2e70eecd354451906 List-Id: CVE: CVE-2026-72276 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: fbdev: metronomefb: fix potential memory leak in metronomefb_probe() Commit: 77e26383083c59a67244fcf2e70eecd354451906 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=77e26383083c59a67244fcf2e70eecd354451906 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72276 Analysis date: Sat, 15 Aug 2026 16:48:56 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: metronomefb_probe may leak deferred IO pageref memory on an initialization error path, but triggering normally requires privileged driver or device management and the issue has no demonstrated memory corruption or privilege escalation impact. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72276 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72276 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-2026-72276 LOW CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;CWE-404;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.1';DESCR 'metronomefb_probe can leak deferred IO pageref memory on an initialization error path because fb_deferred_io_cleanup is not called after fb_deferred_io_init succeeds and fb_alloc_cmap later fails. This is a probe time resource leak rather than a use after free or other memory corruption primitive. For the CVSS the PR:H is used because reliable triggering normally requires administrative control over driver probing, device binding, module handling, or equivalent platform device management. The issue is not network reachable and is not triggered by normal packet or remote input processing. Impact is denial of service only through possible memory exhaustion after repeated failed probe cycles, with no direct confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0) SKIP CVE-2026-72276 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE INIT LEAK ERRORPATH UAF LINUS - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 0 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown Triggered positive signals: * None for practical exploitability. * No remote reachability. * No local unprivileged trigger. * No memory corruption primitive. * No UAF, double-free, OOB write, refcount misuse, type confusion, or stale callback. * No confidentiality or integrity impact. Negative or limiting signals: * Requires admin/root/CAP_* in typical deployments: -2. * Reliable triggering requires control over driver probing, module/device binding, or platform device management. * Rare and difficult-to-reach subsystem/configuration: -1. * metronomefb is a niche fbdev driver and normally requires matching hardware/platform setup. * Resource leak is constrained. * The leak occurs only on a probe error path after fb_deferred_io_init succeeds and fb_alloc_cmap fails. * A single failed probe leaks limited memory and does not imply immediate system-wide failure. ## 3. Reachability analysis The bug is triggered during metronomefb_probe() error handling. A normal unprivileged user cannot usually force this path because probing, binding, unbinding, or reloading this platform framebuffer driver is an administrative operation. Namespaces or containers do not materially lower the requirement in typical deployments unless a container is given unusually broad device-management privileges. The path is not network reachable and is not exposed through normal packet, filesystem, or syscall data-plane input. Realistic exploitation would require repeated failed probe cycles under privileged control to accumulate leaked pageref allocations. That makes it a low-priority resource leak rather than an actionable kernel vulnerability. ## 4. Severity interpretation This behaves like a Low-like or ordinary Moderate cleanup issue, not an Important-class vulnerability. The theoretical impact is memory exhaustion after repeated privileged failed initialization attempts. The realistic impact is limited because the affected path is privileged, hardware-specific, non-default, and does not show memory corruption or security-boundary bypass. ## 5. One-sentence report phrase metronomefb_probe may leak deferred IO pageref memory on an initialization error path, but triggering normally requires privileged driver or device management and the issue has no demonstrated memory corruption or privilege escalation impact. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be handled as an auto-close or deferred low-priority resource leak because it is privileged, rare, non-network-reachable, and lacks a concrete memory corruption or security-boundary bypass primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: fbdev: metronomefb: fix potential memory leak in metronomefb_probe() Commit: 77e26383083c59a67244fcf2e70eecd354451906 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=77e26383083c59a67244fcf2e70eecd354451906 Commit description: The memory allocated for pagerefs in fb_deferred_io_init() is not freed on the error path. Fix it by calling fb_deferred_io_cleanup(). Fixes: 56c134f ("fbdev: Track deferred-I/O pages in pageref struct") Cc: stable@vger.kernel.org Signed-off-by: Abdun Nihaal Reviewed-by: Thomas Zimmermann Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman Changed files: drivers/video/fbdev/metronomefb.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=77e26383083c59a67244fcf2e70eecd354451906 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72276 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72276 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:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.1 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: LOW KPANIC detected for this report: NO 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).