CVE-2026-98629 Linux CVE debrief

Who should care

Defenders responsible for Linux kernel systems using the cls_u32 feature should assess exposure and prioritize verification and patching. This includes operators, platform administrators, vulnerability management teams, and security teams who need to ensure that their systems are up-to-date and secure. They should also monitor for potential exploitation attempts and review system configurations to ensure they are secure.

Why it matters

The vulnerability in the Linux kernel's net/sched: cls_u32 feature can cause issues with manual hash table handle IDR aliasing, leading to potential exploitation. Defenders should prioritize verification and patching, as well as monitoring for potential exploitation attempts.

• Verify and apply patches to prevent potential exploitation
• Monitor for potential exploitation attempts to detect possible attacks
• Review system configurations to ensure they are up-to-date and secure

Technical summary

The vulnerability in the Linux kernel's net/sched: cls_u32 feature is caused by a discrepancy between the raw handle and the handle2id(handle) in the cls_u32 feature. This discrepancy causes issues for handles in the 0x800..0xFFF htid range, leading to a permanent leak of the raw-keyed IDR entry on delete and potential aliasing of live manual tables by later auto allocations. A manual table created with an explicit handle keys its IDR entry on the raw handle, while the destroy paths free it under handle2id(handle). The vulnerability can be resolved by keying the divisor-path alloc on handle2id(handle) so allocation and removal share one key domain. A manual handle that maps onto an id already in use is rejected

Defensive priority

Defenders should prioritize verifying and applying patches for this vulnerability, especially for systems using the Linux kernel with the cls_u32 feature. They should also monitor for potential exploitation attempts.

Recommended defensive actions

• Verify and apply patches for this vulnerability
• Monitor for potential exploitation attempts
• Review system configurations and update as necessary
• Conduct a thorough review of system configurations to ensure they are up-to-date and secure
• Prioritize verification and patching for systems using the Linux kernel with the cls_u32 feature
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The vulnerability was resolved in the Linux kernel. The CVE record and NVD entry provide details about the vulnerability. However, the evidence is limited, and defenders should verify the vulnerability's existence and impact on their systems.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.