CVE-2026-23397 Linux CVE debrief

Who should care

Linux kernel users and administrators should be aware of this vulnerability and take steps to mitigate it. Affected systems include those running Linux kernels with nfnetlink_osf enabled. Security teams should review and apply patches or mitigations as soon as possible.

Technical summary

The vulnerability exists in the nfnetlink_osf component of the Linux kernel. The nfnl_osf_add_callback() function validates opt_num bounds and string NUL-termination but does not check individual option length fields. This can cause nf_osf_match_one() to enter the option matching loop even when foptsize sums to zero, leading to a general protection fault and potential null-pointer dereference. Additionally, an MSS option (kind=2) with length < 4 causes out-of-bounds reads when nf_osf_match_one() unconditionally accesses optp[2] and optp[3] for MSS value extraction.

Defensive priority

High

Recommended defensive actions

• Apply patches from Linux kernel maintainers
• Restrict access to nfnetlink_osf component
• Monitor network traffic for suspicious activity
• Keep Linux kernel up-to-date
• Review compensating controls for exposed systems
• Track exceptions and retest remediated assets
• Verify patch deployment in managed environments

Evidence notes

The CVE record was published on 2026-03-26T11:16:19.720Z and was last modified on 2026-07-14T13:18:32.457Z. The NVD entry is currently Modified. This vulnerability affects Linux kernel users and administrators. Evidence is limited to public CVE and NVD information.

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.