CVE-2026-52999

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nfnetlink_osf: fix out-of-bounds read on option matching

In nf_osf_match(), the nf_osf_hdr_ctx structure is initialized once

and passed by reference to nf_osf_match_one() for each fingerprint

checked. During TCP option parsing, nf_osf_match_one() advances the

shared ctx->optp pointer.

If a fingerprint perfectly matches, the function returns early without

restoring ctx->optp to its initial state. If the user has configured

NF_OSF_LOGLEVEL_ALL, the loop continues to the next fingerprint.

However, because ctx->optp was not restored, the next call to

nf_osf_match_one() starts parsing from the end of the options buffer.

This causes subsequent matches to read garbage data and fail

immediately, making it impossible to log more than one match or logging

incorrect matches.

Instead of using a shared ctx->optp pointer, pass the context as a

constant pointer and use a local pointer (optp) for TCP option

traversal. This makes nf_osf_match_one() strictly stateless from the

caller's perspective, ensuring every fingerprint check starts at the

correct option offset.