CVE-2026-23397
CVE-2026-23397: Buffer Over-read in nfnetlink_osf Fingerprints
Executive Summary
CVE-2026-23397 is a medium severity vulnerability affecting software systems. It is classified as Out-of-bounds Read. Ensure your systems and dependencies are patched immediately to mitigate exposure risks.
Precogs AI Insight
"Precogs AI detected this vulnerability pattern in Out-of-bounds Read implementations. The pattern deviates from documented secure coding standards, suggesting a high likelihood of exploitation if unpatched."
Summary
A medium-severity out-of-bounds read vulnerability (CVE-2026-23397) has been identified in the Linux kernel's nfnetlink_osf module. The nfnl_osf_add_callback() function fails to validate individual option length fields within OS fingerprint structures (CWE-125).
Technical Details
The issue is classified under CWE-125 (Out-of-bounds Read). The nfnetlink_osf module implements passive OS fingerprinting for Netfilter. When adding new fingerprint entries via netlink, the nfnl_osf_add_callback() function validates the overall opt_num bounds and ensures string NUL-termination, but does not validate the length field of each individual option within the fingerprint structure.
A malicious option entry with an oversized length field causes the kernel to read memory beyond the allocated buffer when processing the fingerprint, potentially exposing sensitive kernel data.
Exploitation Context
- Vector: Local
- Authentication: Required (CAP_NET_ADMIN capability)
- Complexity: Low
- Impact: Medium (Confidentiality — kernel memory disclosure)
While exploitation requires local access with network administration capabilities, in containerized environments, CAP_NET_ADMIN is sometimes granted to containers, expanding the attack surface.
Remediation
Linux administrators should immediately:
- Apply the latest kernel patch that adds per-option length validation in
nfnl_osf_add_callback()before processing fingerprint entries. - Review container security policies to ensure CAP_NET_ADMIN is not unnecessarily granted to containerized workloads.
- Consider disabling the
nfnetlink_osfmodule (modprobe -r nf_osf) if passive OS fingerprinting is not required in your environment.
Precogs AI Integration
The Precogs AI Binary Security Platform detects out-of-bounds read conditions by tracing array index and length field usage in kernel netlink message parsers, verifying that all user-supplied size fields are validated against buffer boundaries before being used in memory access operations.