{"cve":"CVE-2026-23397","nvd":{"published":"2026-03-26T11:16:19.720","modified":"2026-10-15T02:18:54.960","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfnetlink_osf: validate individual option lengths in fingerprints\n\nnfnl_osf_add_callback() validates opt_num bounds and string\nNUL-termination but does not check individual option length fields.\nA zero-length option causes nf_osf_match_one() to enter the option\nmatching loop even when foptsize sums to zero, which matches packets\nwith no TCP options where ctx->optp is NULL:\n\n Oops: general protection fault\n KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]\n RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98)\n Call Trace:\n  nf_osf_match (net/netfilter/nfnetlink_osf.c:227)\n  xt_osf_match_packet (net/netfilter/xt_osf.c:32)\n  ipt_do_table (net/ipv4/netfilter/ip_tables.c:293)\n  nf_hook_slow (net/netfilter/core.c:623)\n  ip_local_deliver (net/ipv4/ip_input.c:262)\n  ip_rcv (net/ipv4/ip_input.c:573)\n\nAdditionally, an MSS option (kind=2) with length < 4 causes\nout-of-bounds reads when nf_osf_match_one() unconditionally accesses\noptp[2] and optp[3] for MSS value extraction.  While RFC 9293\nsection 3.2 specifies that the MSS option is always exactly 4\nbytes (Kind=2, Length=4), the check uses \"< 4\" rather than\n\"!= 4\" because lengths greater than 4 do not cause memory\nsafety issues -- the buffer is guaranteed to be at least\nfoptsize bytes by the ctx->optsize == foptsize check.\n\nReject fingerprints where any option has zero length, or where an MSS\noption has length less than 4, at add time rather than trusting these\nvalues in the packet matching hot path.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","score":7.1},"cwes":["CWE-125"],"references":["https://git.kernel.org/stable/c/224f4678812e1a7bc8341bcb666773a0aec5ea6f","https://git.kernel.org/stable/c/3932620c04c2938c93c0890c225960d3d34ba355","https://git.kernel.org/stable/c/3c11b5c2436a3a5b450612ab160e3a525b28cfb5","https://git.kernel.org/stable/c/4c6aa008b913e808c4f4d3cde36cb1d9bb5967c6","https://git.kernel.org/stable/c/aa0574182c46963c3cdb8cde46ec93aca21100d8"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:28:18.033120106+00:00"},"epss":{"cve":"CVE-2026-23397","score":0.00127,"percentile":0.02365,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}