CVE-2026-43190 (GCVE-0-2026-43190)

Vulnerability from cvelistv5 – Published: 2026-05-06 11:27 – Updated: 2026-10-19 19:16
VLAI
Title
netfilter: xt_tcpmss: check remaining length before reading optlen
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: xt_tcpmss: check remaining length before reading optlen Quoting reporter: In net/netfilter/xt_tcpmss.c (lines 53-68), the TCP option parser reads op[i+1] directly without validating the remaining option length. If the last byte of the option field is not EOL/NOP (0/1), the code attempts to index op[i+1]. In the case where i + 1 == optlen, this causes an out-of-bounds read, accessing memory past the optlen boundary (either reading beyond the stack buffer _opt or the following payload).
Severity
8.2 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 15:15 UTC
CWE
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7033 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < f895191dc32c53eaf443b6443fe40945b2f92287 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < cd5beda7e0e32865e214f28034bb92c1cecff885 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < eaedc0bc18be46fe7f58170e967959a932c4f824 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 07a9b32eaae792ff7d0fcac14d8920c937c0a9c3 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 8b300f726640c48c3edfe9c453334dd801f4b74e (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 5e13d0a37666955b6cfddc0f73cb40ed645b8a05 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < f6c412dcfd76b0516d51aa847d8f4c7b70381b09 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 735ee8582da3d239eb0c7a53adca61b79fb228b3 (git)
guessed Create a notification for this product.
Linux Linux Affected: 2.6.12
Unaffected: 0 , < 2.6.12 (semver)
Unaffected: 5.10.252 , ≤ 5.10.* (semver)
Unaffected: 5.15.202 , ≤ 5.15.* (semver)
Unaffected: 6.1.165 , ≤ 6.1.* (semver)
Unaffected: 6.6.128 , ≤ 6.6.* (semver)
Unaffected: 6.12.75 , ≤ 6.12.* (semver)
Unaffected: 6.18.16 , ≤ 6.18.* (semver)
Unaffected: 6.19.6 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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      "product_status:fixed": "2085",
      "product_status:known_affected": "36",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: netfilter: xt_tcpmss: check remaining length before reading optlen",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43190.json",
      "version": "3"
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    "vulnrichment": {
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                  "value": "AV:N - The vulnerable match runs in IPv4/IPv6 netfilter packet-processing hooks, so a remote peer can trigger it by sending a crafted TCP packet to or through a system with a tcpmss iptables/nftables-compatible rule installed.\nAC:L - The trigger is a deterministic TCP option layout where the final option byte is neither EOL nor NOP, causing op[i+1] to be read past the remaining option length. The attacker controls the packet contents and no race or external timing condition is required.\nPR:N - The packet sender does not need credentials or local privileges to reach the rule once it is present on a firewall/router/host. Installing rules requires CAP_NET_ADMIN, including via network namespaces, but that is not required for the remote-trigger scenario.\nUI:N - No victim user action is required; packet processing occurs automatically in the kernel receive/forward/output netfilter path.\nS:U - The impact remains within the kernel/network stack security authority on the affected system. There is no VM escape, IOMMU/DMA boundary crossing, or other scope-changing boundary involved.\nC:L - The bug is a bounded one-byte out-of-bounds read beyond the TCP options buffer, potentially into adjacent stack or skb data. Because it is only a single byte and is not a broad arbitrary read primitive, confidentiality impact is Low rather than High.\nI:N - The vulnerable operation only reads op[i+1] and uses it to advance the parser; it does not write to kernel memory or packet data. I found no control-flow or data-integrity primitive from this one-byte read.\nA:H - Malformed packets can repeatedly trigger the out-of-bounds read in softirq/netfilter packet processing. On instrumented or hardened kernels this can produce a KASAN/oops/panic, so availability impact is High under highest-defensible scoring."
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}



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