From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98237][LOW] net: wwan: mhi_wwan_mbim: guard against a cyclic NDP chain Date: Fri, 09 Oct 2026 12:39:16 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98237 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 2 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 3ed36ee1b29b028f6bc2ebe100152f61a33df05a List-Id: CVE: CVE-2026-98237 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: net: wwan: mhi_wwan_mbim: guard against a cyclic NDP chain Commit: 3ed36ee1b29b028f6bc2ebe100152f61a33df05a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3ed36ee1b29b028f6bc2ebe100152f61a33df05a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98237 Analysis date: Fri, 09 Oct 2026 12:39:16 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98237 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98237 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: LOW Manual review required: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-98237 LOW https://www.kernelcve.org/list/?q=CVE-2026-98237 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both LOW) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';*CWE-835;*CWE-20;**CWE-400;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.6';DESCR 'The MHI WWAN MBIM receive path can enter an infinite loop because NDP traversal previously accepted a next offset that points to the current or an earlier NDP. A malformed NTB supplied by a malicious or compromised modem can keep mhi_mbim_rx running forever, pin one CPU at 100 percent, and prevent the receive thread from returning. For the CVSS the PR:N value is used because the triggering data can originate from the attached modem without a local user account or local code execution on the host. The realistic attack boundary is the physical or virtual MHI device rather than an arbitrary Internet peer because ordinary network traffic does not normally control the NDP metadata produced by modem firmware. The demonstrated impact is denial of service through CPU exhaustion. There is no supported UAF, out of bounds access, information leak, or write primitive, so confidentiality and integrity remain unaffected.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE SIMPLEFIX NETWORK HARDWARE LINUS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 2. * Conservative score: 2. * Raw paranoid score: 2. * Paranoid score: 2. * No floor or cap changed either score. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Firmware-mediated external influence. A malformed NTB generated or supplied by a malicious, compromised, or emulated modem reaches `mhi_mbim_rx()`. * +1 Strong device-path DoS. The supplied test demonstrates an infinite kernel loop, one CPU pinned at 100 percent, and a receive thread that never returns. * No extra Availability point. CPU consumption and the stuck receive path are the same demonstrated consequence. * No direct remote-reachability bonus. An arbitrary network peer is not shown to control MBIM NDP metadata without modem or firmware mediation. * No memory-corruption bonus. The patch establishes no OOB access, UAF, overwrite, stale pointer, or invalid free. * No B5-R promotion. There is no heap OOB write, retry-accumulated write index, or later consumption of corrupted structured state. * No confidentiality, integrity, LPE, controlled-reclaim, or arbitrary-write signals. * No hardware rarity penalty. The path requires MHI WWAN functionality, but the supplied evidence does not establish rare physical-only hardware, and the behavior was also verified under QEMU. * No privilege penalty. Host-admin privilege is not part of the vulnerable receive operation. 3. Reachability analysis The immediate input producer is an attached, compromised, malicious, or emulated MHI modem capable of supplying an NTB with a cyclic NDP chain. This establishes below-host-admin triggering at the device boundary, so `HostAdminRequired=NO`, but it does not establish direct Internet reachability. Ordinary cellular traffic is not shown to control `wNextNdpIndex`, because that structural metadata is normally produced by modem firmware. No network-namespace capability participates in the trigger, so `NamespaceScopedPrivilege=NO`. An MHI WWAN device or equivalent virtual setup and the affected driver are prerequisites. There is no race or narrow timing requirement. A single self-reference deterministically sustains the loop. 4. Primitive and severity interpretation The exact primitive is attacker-influenced invalid traversal state causing a non-terminating loop. It is neither stale storage nor an active structured-object UAF. No release, refcount mutation, OOB write, descriptor corruption, or post-corruption operation is present. This is `CLASS_C` because the demonstrated behavior is a deterministic CPU and receive-thread DoS without an independently useful corruption primitive. The practical consequence is loss of one CPU and failure of the affected receive path. A wider host impact through watchdog policy is possible operationally, but it does not create a separate scored primitive. `ImportantCandidate=NO` because the B5-R requirements fail at the first gate and no memory-corruption or security-boundary primitive exists. `AutoDowngradeAllowed=YES` because automatic Moderate or Low-like handling would not discard unresolved corruption leverage. 5. One-sentence report phrase A malformed cyclic NDP chain supplied through an MHI modem can keep `mhi_mbim_rx()` spinning indefinitely, pinning one CPU and blocking the receive thread without establishing memory corruption or direct network reachability. 6. Manual review recommendation NO MANUAL CHECK NEEDED The issue is a well-defined firmware-mediated infinite-loop DoS with a direct termination fix and no evidence of OOB access, UAF, corrupted-state consumption, authorization bypass, or privilege escalation. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net: wwan: mhi_wwan_mbim: guard against a cyclic NDP chain Commit: 3ed36ee1b29b028f6bc2ebe100152f61a33df05a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3ed36ee1b29b028f6bc2ebe100152f61a33df05a Commit description: The NDP traversal in mhi_mbim_rx() only stops when wNextNdpIndex is zero. Nothing requires the offsets to advance, so a modem that points an NDP at itself, or at an earlier NDP, keeps the loop spinning forever on one CPU. Break out when the next NDP offset is not larger than the current one. Fixes: aa730a9 ("net: wwan: Add MHI MBIM network driver") Cc: stable@vger.kernel.org Suggested-by: Loic Poulain Signed-off-by: Guanglei Zhu Signed-off-by: Greg Kroah-Hartman Verified in a QEMU guest with a fault injector feeding the driver's receive callback an NTB whose single NDP points at itself: the unpatched driver spins in mhi_mbim_rx() with one CPU pinned at 100% and the thread never returns. With this check the loop terminates within one iteration. Changes in v2: move the non-increasing check to the wNextNdpIndex retrieval site, as suggested by Loic Poulain, instead of tracking the previous offset in a separate variable. Link: https://patch.msgid.link/20260911021734.1396599-1-zhugl3@xiaopeng.com Signed-off-by: Jakub Kicinski Changed files: drivers/net/wwan/mhi_wwan_mbim.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=3ed36ee1b29b028f6bc2ebe100152f61a33df05a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98237 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98237 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:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.6 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: 2 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).