From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53076][MODERATE REGULAR] bpf: Fix OOB in pcpu_init_value [ Upstream Date: Wed, 24 Jun 2026 15:36:06 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53076 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: 4 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: e19c5ed9f1922a6854073f8651a63fa7be26e9e9 List-Id: CVE: CVE-2026-53076 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: bpf: Fix OOB in pcpu_init_value [ Upstream Commit: e19c5ed9f1922a6854073f8651a63fa7be26e9e9 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e19c5ed9f1922a6854073f8651a63fa7be26e9e9 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53076 Analysis date: Wed, 24 Jun 2026 15:36:06 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Borderline manual review recommended Manual review required: YES Summary: A local BPF user may trigger a small out-of-bounds read in pcpu_init_value when copying a non 8 byte aligned CGROUP_STORAGE value into a percpu map, potentially causing limited kernel memory disclosure but with no demonstrated write primitive or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53076 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53076 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: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-53076 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L';CWE-125;CWE-126;*CWE-200;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '4.4';DESCR 'An out-of-bounds read can occur in BPF pcpu_init_value because copy_map_value_long copies a value rounded up to an 8 byte boundary even when the source object is only value_size bytes long. A local process can trigger this by using a BPF_MAP_TYPE_CGROUP_STORAGE value whose size is not aligned to 8 bytes, for example 4 bytes, and then copying it into a per CPU map with the same value_size. For the CVSS the PR:L is used because triggering requires local BPF map creation and update capability, which may be available to a local user or delegated service but is not a purely remote action. The issue is not network reachable and does not require user interaction. Impact is primarily a limited confidentiality risk from reading bytes past the source value, with possible low availability impact in hardened or sanitizer builds. No direct arbitrary write or UAF primitive is indicated, so privilege escalation is not assumed from the patch alone.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended (with actual score 4) YES OOB BPF SIMPLEFIX HARDWARE LINUS INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 4 * Final recommended bucket: **Borderline manual review recommended**:: ## 2. Signal breakdown * Local unprivileged or low-privileged trigger: +1 Triggering requires local BPF map creation and update operations. This is not remote, but may be reachable by a local user or delegated service depending on BPF policy. * Local high-control kernel data-plane API: +1 BPF maps allow attacker-controlled value_size, map type selection, and source/destination value movement. Here the bug depends on controlled mismatched rounding behavior between CGROUP_STORAGE and percpu map copy paths. * Confidentiality impact plausible: +1 The primitive is an OOB read of a few bytes beyond the source object. If copied bytes become observable through map state or a related BPF path, this may cause limited kernel memory disclosure. * Broad/common subsystem exposure, paranoid only: +1 BPF is a widely deployed kernel subsystem and historically security-sensitive. This does not make the bug Important by itself, but it supports not auto-closing without review. * Weak read-only OOB primitive: +0 The patch shows an out-of-bounds read, not an OOB write, UAF, double free, type confusion, refcount takeover, or arbitrary write. * No privilege escalation signal: +0 No attacker-controlled overwrite, reclaim, callback dispatch, or object lifetime corruption is shown. * No reliable strong DoS signal: +0 Availability impact is not strongly demonstrated. A sanitizer or hardened build might report a fault, but the ordinary primitive is limited read past the source value. ## 3. Reachability analysis The bug is locally reachable through BPF map operations involving BPF_MAP_TYPE_CGROUP_STORAGE and a percpu map with a value_size not rounded to 8 bytes. It is not network reachable. In many production systems unprivileged BPF is disabled and BPF use requires CAP_BPF, CAP_SYS_ADMIN, or a privileged service, which lowers practical exposure. In environments with delegated BPF access, containers with BPF capability, or developer systems with unprivileged BPF enabled, PR:L is a reasonable practical interpretation. ## 4. Severity interpretation This behaves more like an actionable low-to-moderate BPF information-disclosure candidate than an Important-class memory corruption bug. The theoretical concern is limited kernel memory disclosure from an OOB read caused by 8-byte rounded copying. The realistic evidence does not show write corruption, UAF, controlled object replacement, or privilege escalation. Because the subsystem is BPF and the primitive is an OOB read, manual review is still justified. ## 5. One-sentence report phrase A local BPF user may trigger a small out-of-bounds read in pcpu_init_value when copying a non 8 byte aligned CGROUP_STORAGE value into a percpu map, potentially causing limited kernel memory disclosure but with no demonstrated write primitive or privilege escalation. ## 6. Manual review recommendation MANUAL CHECK REQUIRED This should not be auto-closed because it is a BPF OOB read with plausible limited confidentiality impact, even though the current evidence does not support Important severity or a privilege-escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf: Fix OOB in pcpu_init_value [ Upstream Commit: e19c5ed9f1922a6854073f8651a63fa7be26e9e9 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e19c5ed9f1922a6854073f8651a63fa7be26e9e9 Changed files: kernel/bpf/hashtab.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=e19c5ed9f1922a6854073f8651a63fa7be26e9e9 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53076 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53076 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:L/I:N/A:N The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L The Best / paranoid CVSS score: 4.4 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: 4 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).