From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98588][IMPORTANT] bpf, sockmap: Reject max_entries > INT_MAX in sock_map_alloc [ Upstream Date: Fri, 23 Oct 2026 21:04:05 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98588 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: f4a73f49e256bd835368504462be3b57b03febff List-Id: CVE: CVE-2026-98588 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: NO Patch: bpf, sockmap: Reject max_entries > INT_MAX in sock_map_alloc [ Upstream Commit: f4a73f49e256bd835368504462be3b57b03febff Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f4a73f49e256bd835368504462be3b57b03febff Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98588 Analysis date: Fri, 23 Oct 2026 21:04:05 -0400 ActionableScore: 5 ActionableScore lower bound: unknown Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: A locally created oversized BPF SOCKMAP can overflow the signed cleanup iterator and perform a fixed NULL write about 16 GiB before its allocated array, causing a kernel crash or potentially corrupting an unrelated vmalloc allocation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98588 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98588 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: IMPORTANT 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-2026-98588 IMPORTANT https://www.kernelcve.org/list/?q=CVE-2026-98588 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=3 LEGACY=IMPORTANT RESULT=DIFF INDEPENDENT_LEGACY=IMPORTANT INDEPENDENT_RESULT=DIFF TEMP_KPANIC_MERGE=IMPORTANT_WINS_DISAGREEMENT PRE_MERGE_LEGACY=IMPORTANT (final Legacy and Aegis differ; FINAL: IMPORTANT, Aegis: MODERATE_KPANIC) 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-787;CWE-190;CWE-129;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A signed iterator overflow in sock_map_free can make the cleanup loop access memory about 16 GiB below the allocated sks array when a SOCKMAP is created with max_entries equal to UINT_MAX. The faulting xchg performs an out of bounds NULL write. On KASAN systems this normally causes an Oops during shadow checking, while a non KASAN kernel can fault on an unmapped vmalloc page or corrupt an unrelated populated allocation. Impact is at least a local denial of service through a kernel crash. In the worst case the memory corruption may affect confidentiality and integrity or support privilege escalation, although reliable exploitation would require control over vmalloc placement and a suitable object for the fixed NULL write. For the CVSS the PR:L reflects that a local process must create and destroy the BPF SOCKMAP. Systems that disable unprivileged BPF may additionally require CAP_BPF or an equivalent capability. AC:H reflects the requirement for a host where the approximately 32 GiB allocation succeeds and the relevant vmalloc layout permits the invalid write. The issue is not network reachable. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were KP and FD specialist checks stage IMPORTANT to IMPORTANT because a specific evidence based protection or manual review veto was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were V42_LEGACY_CLASSA_FD_VETO and MANUAL_REVIEW_REQUIRED and TEMP_KPANIC_MERGE_IMPORTANT_WINS. The independent weaker Aegis shadow evaluated CVSS 4.7 and ActionableScore 3 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is IMPORTANT.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE REMOTE WRITE KASAN OOB BPF LINUS V42_LEGACY_CLASSA_FD_VETO MANUAL_REVIEW_REQUIRED TEMP_KPANIC_MERGE_IMPORTANT_WINS - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 PrimitiveClass=CLASS_A RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw conservative score: 3 * Conservative score: 5 * Raw paranoid score: 3 * Paranoid score: 5 * Applied conservative manual-review safety floor: 3 -> 5 because an attacker-influenced kernel OOB write is directly established. * Applied paranoid manual-review safety floor: 3 -> 5. No additional speculative consequence was scored. * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown Positive signals: * +2 Strong corruption primitive. Attacker-selected `max_entries=UINT_MAX` causes signed iterator overflow and an `xchg()` write approximately 16 GiB before the allocated `sks` array. The payload is fixed to NULL and target selection is not demonstrated, but the destination is outside the allocation and may overlap an unrelated populated vmalloc allocation. * +1 Reliable kernel crash or strong DoS. KASAN reproduces an Oops, while a non-KASAN kernel can fault on an unmapped vmalloc page. Negative signals: * No negative privilege score. BPF access restrictions for the complete trigger are unresolved, so host-admin privilege cannot be assumed. * No race penalty. The failure follows deterministic iteration after successful creation and destruction of the oversized map. * No rare-subsystem penalty. BPF privilege gating affects reachability, but it does not weaken the established write primitive. Material signals not awarded: * Controlled target selection, arbitrary payload, controlled reclaim, callback influence, disclosure, and LPE are not demonstrated. * No separate integrity point was awarded because no particular active victim object or protected state modification is identified. * No extra availability point was awarded for the same crash. * Local unprivileged trigger was not awarded because complete below-host-admin SOCKMAP creation is not established. * NEW52 B5-R does not apply. The index does not accumulate across retries or re-entry. It overflows during one destructor traversal. * V33 active-state trust-boundary preservation is not established because no specific corrupted active object, privileged downstream consumer, or guest or namespace boundary is identified. * B3-PENDING and B4-PENDING do not apply. This is neither a shared-backing write nor an authorization decision bypass. 3. Reachability analysis The trigger requires a local process to create a BPF SOCKMAP with `max_entries=UINT_MAX`, obtain a successful allocation of approximately 32 GiB, and then reach map destruction through creation failure, `close()`, or deferred map cleanup. The supplied evidence does not establish whether the evaluated system permits this operation to an ordinary user. Systems with unprivileged BPF disabled may require `CAP_BPF`, `CAP_SYS_ADMIN`, or related permissions. It is also not established that all necessary BPF operations work within an attacker-created user or network namespace. Therefore, both host-admin and namespace-scoped privilege requirements remain unknown. No network trigger, prior device setup, special hardware, or timing race is involved. The main environmental prerequisite is a sufficiently large-memory host where the 32 GiB allocation succeeds and the invalid destination is reachable. This supports high attack complexity in CVSS terms but does not negate the concrete OOB write for actionable triage. 4. Primitive and severity interpretation The exact primitive is a fixed-value kernel OOB write caused by signed iterator overflow. After `i` wraps to `INT_MIN`, pointer arithmetic selects an address far below `stab->sks`, and `xchg(psk, NULL)` attempts to write there. This is not a UAF, repeated release, authorization bypass, or retry-accumulated B5-R case. The immediate operation is cleanup-related, but it performs a real write outside the allocation rather than merely reading stale state or triggering a guard. The demonstrated consequence is a kernel Oops or page fault. Corruption of an unrelated vmalloc allocation is technically supported when the destination is populated. Consumption of a particular corrupted active object and a resulting privilege escalation are unresolved rather than demonstrated. `PrimitiveClass=CLASS_A` is used because an attacker-controlled map dimension directly produces a kernel OOB write outside the allocated object. `ImportantCandidate=YES` preserves this corruption primitive for review. `AutoDowngradeAllowed=NO` is appropriate because automatically treating the issue as crash-only could discard the unresolved possibility of corrupting a live unrelated vmalloc object. The likely operational severity is Actionable Moderate unless manual analysis establishes useful target placement or consumption of the NULL-corrupted state. 5. One-sentence report phrase A locally created oversized BPF SOCKMAP can overflow the signed cleanup iterator and perform a fixed NULL write about 16 GiB before its allocated array, causing a kernel crash or potentially corrupting an unrelated vmalloc allocation. 6. Manual review recommendation MANUAL CHECK REQUIRED The OOB write is confirmed, but BPF privilege scope, practical vmalloc target placement, and consumption of any corrupted live object require manual verification. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf, sockmap: Reject max_entries > INT_MAX in sock_map_alloc [ Upstream Commit: f4a73f49e256bd835368504462be3b57b03febff Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f4a73f49e256bd835368504462be3b57b03febff Changed files: net/core/sock_map.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=f4a73f49e256bd835368504462be3b57b03febff ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98588 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98588 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: unknown 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: IMPORTANT KPANIC detected for this report: NO Published priority for this report (same as in Subject): IMPORTANT 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).