From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64548][MODERATE 7.0] bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data() [ Upstream Date: Mon, 27 Jul 2026 22:31:57 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64548 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 6 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: f1644c9508d24f50dd9e8ebe8d3ba86e0996d2f5 List-Id: CVE: CVE-2026-64548 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data() [ Upstream Commit: f1644c9508d24f50dd9e8ebe8d3ba86e0996d2f5 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f1644c9508d24f50dd9e8ebe8d3ba86e0996d2f5 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64548 Analysis date: Mon, 27 Jul 2026 22:31:57 -0400 ActionableScore: 6 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: An integer overflow in bpf_msg_push_data() can wrap copy + len to a small allocation size and cause an out-of-bounds memcpy in kernel memory, making this a BPF-gated local memory corruption issue with DoS demonstrated and LPE potential requiring manual review. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64548 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64548 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: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-64548 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-190;CWE-680;*CWE-787;CWE-122;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H';BEST CVSS score: '7.8';DESCR 'An integer overflow in bpf_msg_push_data() can make copy and len wrap to a small allocation size when the scatterlist ring is full or nearly full. The helper can then perform an out-of-bounds memcpy into an undersized kernel allocation, which is a concrete memory corruption primitive rather than a DoS-only condition. For the CVSS the PR:L is used for the paranoid score because BPF and sockmap access may be available to a local low privileged user in some deployments through delegated CAP_BPF, CAP_NET_ADMIN, container root, service accounts, or unprivileged BPF configurations. The issue is local and is not directly network reachable because the attacker must control the BPF helper arguments or the local program path that invokes them. Impact is at least a local denial of service via kernel crash and in worst case may allow confidentiality, integrity, and availability impact due to kernel memory corruption. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) YES REMOTE WRITE KASAN OOB BPF KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=6 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 6 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Generic memory corruption, strong corruption primitive: +2. The patch fixes a u32 overflow in copy + len that can cause undersized allocation followed by out-of-bounds memcpy. * Privilege escalation plausible: +2. Heap/OOB write in kernel memory is a plausible LPE class, even though no reliable exploit primitive is demonstrated. * Memory layout invariant restoration: +1. The fix restores consistency between allocation size and later copy length. * Reliable kernel crash / strong DoS: +1. The commit includes a KASAN/Oops trace from __asan_memcpy. * Requires admin/root/CAP_* in typical deployments: -2. Loading and attaching the relevant BPF sockmap/sk_msg program usually requires CAP_BPF, CAP_NET_ADMIN, CAP_SYS_ADMIN, or root-controlled BPF configuration. Conservative total: 4. Paranoid interpretation: * Treat BPF/sockmap access as PR:L if available to container root, delegated CAP_BPF/CAP_NET_ADMIN, service accounts, or systems with unprivileged BPF enabled. * Add local low-privilege reachability and high-control BPF data-plane relevance, but apply the BPF gating cap. * Paranoid score is capped at 6 because the issue is BPF-gated and there is no demonstrated unprivileged exploit, arbitrary write, or working LPE. ## 3. Reachability analysis The bug is local, not directly network reachable. The attacker must control a BPF sk_msg/sockmap program path that calls bpf_msg_push_data() with a crafted len while the scatterlist ring is full or nearly full. In typical hardened/product configurations, this requires privileged BPF access and should be treated as PR:H or privileged local. In less restrictive deployments, delegated BPF/network capabilities, container root with relevant capabilities, or unprivileged BPF settings may reduce this to PR:L. The affected path is not a generic packet receive path. Network traffic may help exercise the sendmsg path, but the key attacker control is through the BPF helper arguments and program attachment. Call-site confidence: high. The commit provides the helper, the overflow site, and a concrete call trace through sk_psock_msg_verdict(), tcp_bpf_sendmsg(), and sendto(). ## 4. Severity interpretation This is not an ordinary Moderate DoS-only issue. The patch describes a concrete integer overflow leading to undersized allocation and out-of-bounds memcpy, which is a real kernel memory corruption primitive. Realistic exploitation is limited by BPF privilege gating, so the conservative score remains below Important. However, because the corruption primitive is concrete and BPF reachability can vary significantly across deployments, it should be treated as Actionable Moderate at minimum and an Important candidate under PR:L assumptions. Theoretical impact includes privilege escalation due to kernel heap corruption. Realistic evidence currently demonstrates crash/Oops, not a working LPE. ## 5. One-sentence report phrase An integer overflow in bpf_msg_push_data() can wrap copy + len to a small allocation size and cause an out-of-bounds memcpy in kernel memory, making this a BPF-gated local memory corruption issue with DoS demonstrated and LPE potential requiring manual review. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the patch shows a concrete kernel OOB memcpy primitive, and although typical BPF privilege gating lowers practical exposure, the bug class is memory corruption with plausible privilege-escalation relevance. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data() [ Upstream Commit: f1644c9508d24f50dd9e8ebe8d3ba86e0996d2f5 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f1644c9508d24f50dd9e8ebe8d3ba86e0996d2f5 Changed files: mm/kasan/shadow.c net/core/filter.c net/core/skmsg.c net/ipv4/tcp_bpf.c net/socket.c arch/x86/entry/syscall_64.c arch/x86/entry/entry_64.S 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=f1644c9508d24f50dd9e8ebe8d3ba86e0996d2f5 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64548 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64548 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:H/I:H/A:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7.8 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: 4 Paranoid ActionableScore: 6 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: YES 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).