CVE-2026-23397nfnetlink_osf: validate individual option lengths in fingerprints
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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.
- CVSS
- 7.1 HIGH (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Modified
- Record last updated
- Oct 15, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 before e9cf17b91e733fec725ebcc0b3098bc5ccd505e0; 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 builds before 3c11b5c2436a3a5b450612ab160e3a525b28cfb5; from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 before aa0574182c46963c3cdb8cde46ec93aca21100d8; from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 before 224f4678812e1a7bc8341bcb666773a0aec5ea6f; from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 before ec8bf0571b142f29dc0b68ae2ac3952f7a464b38; from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 before 3932620c04c2938c93c0890c225960d3d34ba355; 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 builds before 4c6aa008b913e808c4f4d3cde36cb1d9bb5967c6; from 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 before dbdfaae9609629a9569362e3b8f33d0a20fd783c | CNA record |
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem siemens:simatic_s7_1500_tm_mfp_gnu_linux_subsystem (from the name) | all versions | CISA ADP |
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
linux linux_kernel linux:linux_kernel | from 2.6.31.1 before 5.10.253; from 5.11 before 5.15.203; from 5.16 before 6.1.167; from 6.2 before 6.6.130; from 6.7 before 6.12.78; from 6.13 before 6.18.20; from 6.19 before 6.19.10; 2.6.31; and 7 more ranges | NVD |
References
- https://git.kernel.org/stable/c/e9cf17b91e733fec725ebcc0b3098bc5ccd505e0patch
- https://git.kernel.org/stable/c/3c11b5c2436a3a5b450612ab160e3a525b28cfb5patch
- https://git.kernel.org/stable/c/aa0574182c46963c3cdb8cde46ec93aca21100d8patch
- https://git.kernel.org/stable/c/224f4678812e1a7bc8341bcb666773a0aec5ea6fpatch
- https://git.kernel.org/stable/c/ec8bf0571b142f29dc0b68ae2ac3952f7a464b38patch
- https://git.kernel.org/stable/c/3932620c04c2938c93c0890c225960d3d34ba355patch
- https://git.kernel.org/stable/c/4c6aa008b913e808c4f4d3cde36cb1d9bb5967c6patch
- https://git.kernel.org/stable/c/dbdfaae9609629a9569362e3b8f33d0a20fd783cpatch
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html
- https://cert-portal.siemens.com/productcert/html/ssa-784472.html
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.