Linux vulnerability

What happened

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.

Affected versions

Linux: 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b through before 0145548346c4a30981a870a8ca00eac46ba27e85 (git); 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b through before 1c136f2c44a5913646bac85303612fd0825197a0 (git); 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b through before 1e19a07291bb8682c14c39a64725a3ae54ab8ccc (git); 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b through before 32e50f92c7cf3f4eba29622179a5fcdc2aebab41 (git); 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b through before 70a3f31d25cf2ec9d4ddfa408120171ead955623 (git); 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b through before 21883587593d7c8bb519a79460a0b5bc5ffbdabd (git); 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b through before edb78a142d2e5948e63647c0646aa7e7886935f0 (git); 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b through before f5ca450087c3baf3651055e7a6de92600f827af3 (git); 0c1054e0e5fdef2369fb089e94def978bd209e1f (git); 8316b60582facd4068fb0916c4db2418c21b7174 (git); 4.19.26 through before 4.20 (semver); 4.20.13 through before 4.21 (semver); 5.0; V3.1.6 through before * (custom) Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.