CVE-2026-23397nfnetlink_osf: validate individual option lengths in fingerprints

Description

In the Linux kernel, the following vulnerability has been resolved: nfnetlink_osf: validate individual option lengths in fingerprints nfnl_osf_add_callback() validates opt_num bounds and string NUL-termination but does not check individual option length fields. A zero-length option causes nf_osf_match_one() to enter the option matching loop even when foptsize sums to zero, which matches packets with no TCP options where ctx->optp is NULL: Oops: general protection fault KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98) Call Trace: nf_osf_match (net/netfilter/nfnetlink_osf.c:227) xt_osf_match_packet (net/netfilter/xt_osf.c:32) ipt_do_table (net/ipv4/netfilter/ip_tables.c:293) nf_hook_slow (net/netfilter/core.c:623) ip_local_deliver (net/ipv4/ip_input.c:262) ip_rcv (net/ipv4/ip_input.c:573) 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. While RFC 9293 section 3.2 specifies that the MSS option is always exactly 4 bytes (Kind=2, Length=4), the check uses "< 4" rather than "!= 4" because lengths greater than 4 do not cause memory safety issues -- the buffer is guaranteed to be at least foptsize bytes by the ctx->optsize == foptsize check. Reject fingerprints where any option has zero length, or where an MSS option has length less than 4, at add time rather than trusting these values in the packet matching hot path.

Timeline

Scores

EPSS (exploitation in 30 days)

0.13% · top 97% of all CVEs (13 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.1.

Affected products

• Linux · Linux

  • affected 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 – < e9cf17b91e733fec725ebcc0b3098bc5ccd505e0
  • affected 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 – < 3c11b5c2436a3a5b450612ab160e3a525b28cfb5
  • affected 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 – < aa0574182c46963c3cdb8cde46ec93aca21100d8
  • affected 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 – < 224f4678812e1a7bc8341bcb666773a0aec5ea6f
  • affected 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 – < ec8bf0571b142f29dc0b68ae2ac3952f7a464b38
  • affected 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 – < 3932620c04c2938c93c0890c225960d3d34ba355
  • affected 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 – < 4c6aa008b913e808c4f4d3cde36cb1d9bb5967c6
  • affected 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 – < dbdfaae9609629a9569362e3b8f33d0a20fd783c

• Linux · Linux

  • affected 2.6.31
  • unaffected < 2.6.31
  • unaffected 5.10.253 – ≤ 5.10.*
  • unaffected 5.15.203 – ≤ 5.15.*
  • unaffected 6.1.167 – ≤ 6.1.*
  • unaffected 6.6.130 – ≤ 6.6.*
  • unaffected 6.12.78 – ≤ 6.12.*
  • unaffected 6.18.20 – ≤ 6.18.*
  • unaffected 6.19.10 – ≤ 6.19.*
  • unaffected 7.0 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-16157 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-23397](https://cveledger.app/badge/CVE-2026-23397.svg)](https://cveledger.app/cve/CVE-2026-23397)

Record last updated 10 Nov 2026, 12:42 UTC.