CVE-2026-98405 Linux CVE debrief

Who should care

Linux kernel developers, administrators responsible for maintaining and securing Linux-based systems, vulnerability management teams, and security teams should review and apply the provided patches to prevent exploitation. They should also monitor system logs for potential exploitation attempts and review compensating controls for exposed systems.

Why it matters

The Linux kernel's SMB client implementation is vulnerable to out-of-bounds reads, which could allow for potential exploitation and compromise of Linux-based systems. Linux kernel developers and administrators should review and apply the provided patches to prevent exploitation.

• Potential for out-of-bounds reads into adjacent kernel memory
• Possible exploitation by a server providing an inflated out_len value
• Need for patching and updating the Linux kernel to prevent exploitation

Technical summary

The Linux kernel's SMB client implementation is vulnerable to out-of-bounds reads due to a missing bounds check in the `parse_posix_sids()` function. This can be exploited by a server providing an inflated `out_len` value, causing the `sidsbuf_end` pointer to point past the end of the received iov. The vulnerability affects Linux kernel developers and administrators responsible for maintaining and securing Linux-based systems. The fix involves rejecting responses where the calculated sidsbuf_end would exceed the received iov boundaries or cause pointer wraparound.

Defensive priority

Medium

Recommended defensive actions

• Review and apply the provided patches to the Linux kernel
• Ensure that the Linux kernel is updated to a version that includes the fix
• Monitor system logs for potential exploitation attempts
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability is described in the Linux kernel's SMB client implementation. The `parse_posix_sids()` function does not properly validate the server-supplied `out_len` value, which can cause the `sidsbuf_end` pointer to point past the end of the received iov. This can lead to out-of-bounds reads into adjacent kernel memory.

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.