From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74720][MODERATE 7.0] bpf: Preserve pointer state for commuted arithmetic [ Upstream Date: Sat, 22 Aug 2026 11:58:58 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74720 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: 2 X-AL-KERNEL-Commit: 86b203aadc2930e0a4f9c6277b5b80ff3664c472 List-Id: CVE: CVE-2026-74720 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: bpf: Preserve pointer state for commuted arithmetic [ Upstream Commit: 86b203aadc2930e0a4f9c6277b5b80ff3664c472 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=86b203aadc2930e0a4f9c6277b5b80ff3664c472 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74720 Analysis date: Sat, 22 Aug 2026 11:58:58 -0400 ActionableScore: 5 ActionableScore lower bound: 2 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A BPF verifier pointer provenance bug in commuted scalar plus pointer arithmetic may allow an accepted program to carry inconsistent pointer state, and although typical deployments require privileged BPF loading, verifier soundness impact makes this an actionable manual-review candidate. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74720 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74720 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-2026-74720 MODERATE CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-20;CWE-823;CWE-119;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'BPF verifier pointer provenance can be corrupted during commuted scalar and pointer arithmetic because scalar plus pointer used to copy only selected fields from the source pointer register into the destination register. For PTR_TO_STACK and other pointer types, provenance is carried by multiple bpf_reg_state fields such as frame number and parent identity, so partial copying can leave the verifier with an inconsistent pointer state. For the CVSS the PR:L value is used because a local user or process needs the ability to load a BPF program, while full root privileges are not assumed when BPF loading is delegated or unprivileged BPF is enabled. The issue is not network reachable and requires local BPF program submission. Impact is at least local denial of service, and in the paranoid view it may allow confidentiality and integrity impact or privilege escalation due to verifier unsoundness and possible unsafe pointer access.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES INIT BPF SIMPLEFIX LINUS INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Memory corruption, weak/indirect corruption candidate: +1 The patch fixes incomplete propagation of BPF pointer provenance in `bpf_reg_state`. This can create an inconsistent verifier model, but the patch does not show a concrete arbitrary read, arbitrary write, reclaim primitive, or controlled object confusion. * Broad/common subsystem: +1 BPF verifier bugs affect a security-critical and broadly deployed kernel subsystem. * Requires admin/root/CAP_* in typical deployments: -2 In the evaluated configuration, loading BPF programs is gated by privileged access such as root, CAP_BPF, CAP_SYS_ADMIN, CAP_NET_ADMIN, or root-controlled sysctls. Therefore unprivileged BPF reachability should not be assumed. Paranoid additional signals: * Weak LPE concern: +1 BPF verifier soundness bugs can sometimes allow unsafe pointer access if the verifier accepts a program with incorrect pointer provenance. This is plausible enough for manual review, but not strong enough to claim a proven LPE primitive. * Confidentiality impact plausible: +1 If verifier state confusion permits unsafe pointer reads, limited kernel memory disclosure could be possible in a worst-case interpretation. * Integrity impact plausible: +1 If verifier state confusion permits unsafe pointer writes, limited integrity impact or privilege escalation could be possible in a worst-case interpretation. * Availability impact plausible: +1 Incorrect verifier acceptance may also lead to kernel crash or verifier/runtime inconsistency. BPF privilege gating cap applied: * Because BPF loading is privileged in the target product configuration and no working exploit, arbitrary read/write, unprivileged trigger, or cross-namespace escape is demonstrated, the paranoid score is capped in the Actionable Moderate range. ## 3. Reachability analysis The bug is triggered through local BPF program submission that exercises commuted arithmetic of the form `scalar += pointer`. It is not network reachable. In typical hardened or enterprise deployments, unprivileged BPF is disabled and loading or attaching relevant BPF programs requires privileged capabilities or root-controlled configuration, so the conservative reachability is privileged local only. Namespaces and containers matter if BPF loading is delegated to a reduced-capability service, container root, or privileged net namespace. In that case the practical PR may be closer to reduced local privilege than full host root, which supports the paranoid score and manual review. No evidence in the supplied patch proves direct unprivileged reachability in the evaluated product. Call-site confidence: high. The patch includes the relevant verifier call path from `adjust_reg_min_max_vals()` into `adjust_ptr_min_max_vals()` and shows how the temporary offset register is used to preserve the scalar operand. ## 4. Severity interpretation This is not an ordinary crash-only Moderate. It is a BPF verifier correctness issue affecting pointer provenance tracking, which is security-sensitive because verifier unsoundness can sometimes become unsafe kernel memory access. Conservatively, the patch only proves inconsistent verifier state and does not demonstrate a concrete arbitrary read, arbitrary write, attacker-controlled object replacement, or privilege escalation chain. Therefore the lower score remains low to borderline. Paranoid interpretation places it in Actionable Moderate because BPF verifier bugs historically require manual scrutiny, and the inconsistency affects pointer identity fields such as stack frame number and parent state. It should not be auto-closed without review, but it is not a Strong Important candidate unless unprivileged reachability or a concrete memory access primitive is demonstrated. ## 5. One-sentence report phrase A BPF verifier pointer provenance bug in commuted scalar plus pointer arithmetic may allow an accepted program to carry inconsistent pointer state, and although typical deployments require privileged BPF loading, verifier soundness impact makes this an actionable manual-review candidate. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: BPF verifier soundness bugs can be underestimated from the patch text alone. The supplied diff does not prove a working LPE primitive, but the affected state includes pointer provenance fields that directly influence memory safety decisions. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf: Preserve pointer state for commuted arithmetic [ Upstream Commit: 86b203aadc2930e0a4f9c6277b5b80ff3664c472 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=86b203aadc2930e0a4f9c6277b5b80ff3664c472 Changed files: kernel/bpf/verifier.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=86b203aadc2930e0a4f9c6277b5b80ff3664c472 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74720 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74720 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:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 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: 2 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).