CVE-2026-74739 Linux CVE debrief

Who should care

Linux administrators and security teams should be aware of this vulnerability and take necessary actions to mitigate it. They should prioritize verifying the integrity of their Linux kernel versions and applying patches to prevent potential exploitation. Additionally, they should review system configurations, monitor system logs, and implement compensating controls for exposed systems.

Why it matters

Linux administrators and security teams should prioritize verifying the integrity of their Linux kernel versions and applying patches to mitigate this vulnerability.

• Potential slab-out-of-bounds read vulnerability
• Possible system crashes or instability
• Potential for attackers to exploit this vulnerability

Technical summary

The vulnerability exists in the Linux kernel's net/sched: cls_u32 component, specifically in the u32_bind_class() function. An unconditionally cast of the passed fh to tc_u_knode and access to &n->res can result in a slab-out-of-bounds read of res->classid in tc_cls_bind_class(). This can be triggered by specific network traffic patterns, potentially allowing attackers to exploit the vulnerability. The vulnerability can be mitigated by verifying the integrity of Linux kernel versions and applying patches. Linux administrators and security teams should prioritize this mitigation.

Defensive priority

Linux administrators and security teams should prioritize verifying the integrity of their Linux kernel versions and applying patches to mitigate this vulnerability.

Recommended defensive actions

• Verify Linux kernel versions and apply patches
• Review system configurations and update as necessary
• Monitor system logs for potential exploitation attempts
• Perform vulnerability scanning to identify potentially affected systems
• Implement compensating controls for exposed systems
• Track exceptions and retest remediated assets
• technicalSummary

Evidence notes

The CVE record and associated source item provide details on the vulnerability, including its description, affected versions, and references to source code changes. The Linux kernel's net/sched: cls_u32 component is vulnerable to a slab-out-of-bounds read. The vulnerability is caused by the u32_bind_class() function unconditionally casting the passed fh to tc_u_knode and accessing &n->res. This can result in a slab-out-of-bounds read of res->classid in tc_cls_bind_class().

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.