From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98581][MODERATE REGULAR] nfc: llcp: Fix list corruption / refcount desync in nfc_llcp_recv_dm() [ Upstream Date: Sat, 24 Oct 2026 07:17:58 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98581 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: 3 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: dd2d24add86b3b63cd87cf2feff98ae119ba19a6 List-Id: CVE: CVE-2026-98581 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: nfc: llcp: Fix list corruption / refcount desync in nfc_llcp_recv_dm() [ Upstream Commit: dd2d24add86b3b63cd87cf2feff98ae119ba19a6 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dd2d24add86b3b63cd87cf2feff98ae119ba19a6 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98581 Analysis date: Sat, 24 Oct 2026 07:17:58 -0400 ActionableScore: 3 ActionableScore lower bound: unknown Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: An unprivileged local LLCP race can corrupt socket-list bookkeeping and leak kernel socket objects until memory exhaustion, without a demonstrated UAF or attacker-directed overwrite. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98581 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98581 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-2026-98581 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98581 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=MODERATE RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-362;*CWE-401;*CWE-664;CWE-667;Other CVSS 'AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.8';DESCR 'A race in nfc_llcp_recv_dm can leave an LLCP socket physically linked on connecting_sockets after its state changes to LLCP_CLOSED. A concurrent release then removes the node under the wrong list lock while connect can modify the same hlist, causing list bookkeeping corruption and a reference count desynchronization that can retain kernel socket objects without bound. For the CVSS the PR:L value is selected because reliable triggering requires an unprivileged local process able to create and operate LLCP sockets. AV:A reflects the additional requirement for a nearby NFC peer to return DM(NOBOUND) or DM(REJ), and AC:H reflects the required race window. The demonstrated primitive is a persistent reference leak with potential memory exhaustion rather than a proven UAF or arbitrary write, so confidentiality and integrity remain N while paranoid availability is H. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 4.8 and the production ActionableScore returned 3 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. The independent weaker Aegis shadow evaluated CVSS 5.0 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) MAYBE RACE LEAK UAF LINUS - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 PrimitiveClass=CLASS_B RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 3. * Conservative score: 3; no floor or cap applied. * Raw paranoid score: 3. * Paranoid score: 3; no additional exploit primitive is supported. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown * +1 local unprivileged trigger: the commit explicitly identifies an unprivileged local process operating LLCP sockets. * +1 weak/indirect active-state corruption: wrong-lock removal races with insertion on the same `connecting_sockets` hlist, corrupting list bookkeeping and desynchronizing membership references. * +1 concrete persistent kernel reference leak: the stated mis-decrement follows the non-freeing `__sock_put()` path, retaining socket objects. * +1 strong DoS: repeated leaked sockets can exhaust kernel memory. * -1 hard race: reliable triggering requires concurrent release/connect activity in the vulnerable window; the supplied evidence explicitly assesses AC:H. Not awarded: * No real UAF: the documented vulnerable outcome is a non-freeing reference mismatch, not demonstrated post-free access. * No repeated-release signal: an exact dangling reference receiving a second lifetime mutation is not shown. * No controlled reclaim, attacker-directed overwrite, arbitrary write, disclosure, or integrity impact. * No remote-reachability bonus: a nearby peer supplies DM, but the complete trigger also requires local LLCP socket operations. * B5-R does not apply: there is no retry-accumulated heap OOB write or later consumption of OOB-corrupted descriptors. * B4 does not apply: no authorization DENY-to-ALLOW transition exists. 3. Reachability analysis The complete trigger is below host-administrator privilege according to the commit: an unprivileged local process operates LLCP sockets while a nearby NFC peer supplies DM(NOBOUND) or DM(REJ). No capability, namespace privilege, UID 0, prior host-admin setup, or unusual hardware beyond an NFC/LLCP link is identified. Trigger reliability depends on winning the release/connect race. 4. Primitive and severity reading The primitive is concurrent corruption of an active socket hlist’s bookkeeping and associated reference-count pairing. It is CLASS_B object/list-state corruption, but the supplied analysis narrows the demonstrated consequence to a persistent non-freeing socket leak and memory-exhaustion DoS. No stale freed object, useful post-free mutation, or non-crash security-boundary effect is shown. Therefore ImportantCandidate is NO and automatic Important preservation is unwarranted, though review is advisable because active kernel list state is corrupted. 5. One-sentence report phrase An unprivileged local LLCP race can corrupt socket-list bookkeeping and leak kernel socket objects until memory exhaustion, without a demonstrated UAF or attacker-directed overwrite. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm race reproducibility and whether malformed hlist state can produce effects beyond the documented persistent reference leak. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: nfc: llcp: Fix list corruption / refcount desync in nfc_llcp_recv_dm() [ Upstream Commit: dd2d24add86b3b63cd87cf2feff98ae119ba19a6 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dd2d24add86b3b63cd87cf2feff98ae119ba19a6 Changed files: net/nfc/llcp_core.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=dd2d24add86b3b63cd87cf2feff98ae119ba19a6 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98581 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98581 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:A/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.8 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: unknown Paranoid ActionableScore: 3 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).