CVE-2026-99064 Linux CVE debrief

Who should care

Defenders responsible for Linux kernel security, network administrators handling network packets with CIPSO options, and teams managing Linux-based systems should assess exposure and prioritize patching.

Why it matters

Defenders should prioritize verifying and applying patches for Linux kernel versions affected by this vulnerability, particularly those handling network packets with CIPSO options, to prevent potential issues with packet handling and option interpretation.

• Incorrect handling of network packets with CIPSO options
• Potential for interpreting packet data as option lengths
• Copying data into fixed-size option storage
• Verification of Linux kernel versions and patches required

Technical summary

The Linux kernel's CIPSO implementation does not adjust cached option offsets when removing CIPSO data, potentially causing incorrect handling of subsequent options. This can lead to issues such as interpreting packet data as option lengths and copying it into fixed-size option storage. To address this, patches have been developed that adjust the cached offsets for options following CIPSO data, ensuring correct handling and preventing potential security issues. The patches modify the cipso_v4_skbuff_delattr function to subtract the CIPSO length from the offsets of subsequent options, such as SRR, RR, TS, and Router Alert.

Defensive priority

Defenders should prioritize verifying and applying patches for Linux kernel versions affected by this vulnerability, particularly those handling network packets with CIPSO options.

Recommended defensive actions

• Verify and apply patches for affected Linux kernel versions
• Review network packet handling for CIPSO options
• Monitor for unusual network activity
• Conduct a thorough review of network packet handling for CIPSO options in Linux kernel versions
• Verify Linux kernel versions and prioritize patching for systems handling network packets with CIPSO options
• Implement 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 CVE record and source item provide details on the vulnerability, including its description, affected versions, and references to kernel patches. However, specific details about exploitation or victim impact are not provided.

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.