From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98805][IMPORTANT] tipc: prevent GCM nonce reuse on peer key changes [ Upstream Date: Mon, 19 Oct 2026 00:11:15 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98805 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: 7 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 5c8ce13c792e28d56f9ec3cd6728d8225bc0e3a2 List-Id: CVE: CVE-2026-98805 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: NO Patch: tipc: prevent GCM nonce reuse on peer key changes [ Upstream Commit: 5c8ce13c792e28d56f9ec3cd6728d8225bc0e3a2 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5c8ce13c792e28d56f9ec3cd6728d8225bc0e3a2 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98805 Analysis date: Mon, 19 Oct 2026 00:11:15 -0400 ActionableScore: 7 ActionableScore lower bound: unknown Actionable bucket: Strong Important candidate Manual review required: YES Summary: TIPC may reuse an AES-GCM nonce after a peer key-status change while retaining the same TX key, enabling an adjacent on-path attacker to compromise traffic confidentiality and forge authenticated packets. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98805 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98805 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-2026-98805 IMPORTANT https://www.kernelcve.org/list/?q=CVE-2026-98805 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT IMPORTANT AEGIS_AS=7 LEGACY=IMPORTANT RESULT=SAME (final reconciliation agrees; DECISION: both IMPORTANT) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';CWE-323;CWE-327;CWE-347;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L';BEST CVSS score: '7.5';DESCR 'TIPC encryption can reuse an AES GCM nonce when a peer reports a receive key change because the per peer counter is reset while the same TX key and salt may remain active. Reusing a key and nonce breaks GCM confidentiality and can expose the authentication key, allowing an attacker to modify captured ciphertext and generate a valid authentication tag. For the CVSS the PR:N applies to an adjacent on path attacker who does not need an account on the affected node, although obtaining a repeated nonce and influencing or observing the required peer key transition increases attack complexity. The attack is network adjacent rather than generally Internet reachable because TIPC is normally deployed between nodes in the same cluster or trusted network segment. Impact includes disclosure of protected traffic and authenticated packet forgery. Availability impact depends on the role of the forged TIPC messages and may range from disrupted communication to a broader cluster service outage. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 7.5 and the production ActionableScore returned 7 with recommendation Strong Important candidate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the ActionableScore threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to IMPORTANT because the ActionableScore threshold rule was applied. final reconciliation stage IMPORTANT to IMPORTANT because KP specialist did not establish a qualifying panic. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. 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 INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 and INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 and KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS 6.9 and ActionableScore 7 with primitive class CLASS_A and manual review REQUIRED. Its independently reconciled impact was IMPORTANT. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is IMPORTANT.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate (with actual score 7) MAYBE WARNONLY TIPC IMPROVEONLY LINUS PACKET INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 KPANIC_UNSUPPORTED_REMOVED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=7 PrimitiveClass=CLASS_A RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=CONFIRMED B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw conservative score: 7 * Conservative score: 7 * Raw paranoid score: 7 * Paranoid score: 7 * No floor or cap was applied. * Final recommended bucket: **Strong Important candidate**:: 2. Signal breakdown Positive signals: * +2 Direct network trigger. Attacker-observable TIPC traffic and peer key-status transitions reach the vulnerable nonce-generation behavior over the cluster network. * +2 Strong exploitation leverage. AES-GCM nonce reuse under the same key exposes a concrete cryptographic primitive for authentication-key recovery and valid ciphertext forgery. * +1 Practical exploit chain. The supplied evidence directly connects nonce reuse to CTR-based ciphertext modification and generation of a valid authentication tag. * +1 Confidentiality impact. Reuse of the same GCM key and nonce exposes relationships between protected plaintexts and breaks the confidentiality guarantee. * +1 Integrity impact. The recovered authentication capability permits modified ciphertext to pass GCM authentication. Non-awarded signals: * No UAF, OOB access, arbitrary kernel write, controlled reclaim, or memory-corruption point was awarded. * No availability point was awarded. Forged TIPC messages may disrupt cluster communication, but a reliable host crash or broad outage is not demonstrated. * No LPE point was awarded. The primitive compromises protected TIPC traffic but does not establish local privilege escalation. * No additional authorization-bypass point was awarded. This is a cryptographic authentication failure, not an omitted kernel DENY-to-ALLOW permission check. * No race penalty was applied. The vulnerable transition requires a peer key-status change, but no narrow or externally uncontrollable timing window is established. * B5-R, B3-PENDING, B4-PENDING, V32, V33, and V34 do not apply. 3. Reachability analysis The principal attacker model is an adjacent on-path actor able to observe and modify traffic between encrypted TIPC nodes. The attacker does not require a local account, host UID 0, a namespace capability, or host-administrator authority on the affected node. Encrypted TIPC and its keys must already have been configured by an administrator. That is a deployment prerequisite rather than an attacker privilege for exploitation of an existing cluster. TIPC is normally limited to a cluster or trusted internal network, so this is adjacent-network exposure rather than general Internet reachability. A peer key-status transition is required to reset the vulnerable per-peer counter while the same TX key remains installed. An on-path attacker may wait for such a transition. Actively inducing it could require control of a valid peer or additional protocol influence not fully established by the supplied context. This condition supports high attack complexity but does not remove the concrete cryptographic primitive once nonce reuse occurs. There is no special hardware, local ioctl, user-namespace, or race prerequisite. 4. Primitive and severity interpretation The exact primitive is reuse of an AES-GCM nonce with the same TX key and salt. The per-peer `sndnxt` counter was reset when peer receive-key state changed, while the sender could continue using the existing TX key. Later packets could therefore repeat earlier key and nonce pairs. This is neither stale storage nor a lifetime violation. It is an active cryptographic-state consistency failure. The supplied commit explicitly establishes confidentiality loss, exposure of the GCM authentication key, ciphertext malleability, and computation of valid tags for forged packets. PrimitiveClass is CLASS_A because a concrete confidentiality and authentication boundary is defeated and a practical forgery primitive is established. The demonstrated consequences are protected-traffic analysis and authenticated packet modification. Broader cluster compromise, host panic, local privilege escalation, and arbitrary kernel memory access remain unproven. ImportantCandidate is YES because this is a direct cryptographic protection failure with meaningful network-adjacent exploitation leverage. AutoDowngradeAllowed is NO because reducing it to ordinary Moderate would discard the established authentication-key and packet-forgery consequences. AuthorizationDecisionBypass is NO because no kernel authorization predicate changes from DENY to ALLOW. ProtectedResourceImpact is CONFIRMED because encrypted and authenticated TIPC traffic is the specifically identified protected resource. 5. One-sentence report phrase TIPC may reuse an AES-GCM nonce after a peer key-status change while retaining the same TX key, enabling an adjacent on-path attacker to compromise traffic confidentiality and forge authenticated packets. 6. Manual review recommendation MANUAL CHECK REQUIRED Confirm affected versions, encrypted TIPC deployment exposure, whether unauthenticated actors can induce peer key-status transitions, and which control or application messages can be forged after authentication-key recovery. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: tipc: prevent GCM nonce reuse on peer key changes [ Upstream Commit: 5c8ce13c792e28d56f9ec3cd6728d8225bc0e3a2 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5c8ce13c792e28d56f9ec3cd6728d8225bc0e3a2 Changed files: net/tipc/crypto.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=5c8ce13c792e28d56f9ec3cd6728d8225bc0e3a2 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98805 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98805 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:N/UI:N/S:U/C:H/I:H/A:L The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7.5 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: 7 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).