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).

Timeline

1. May 6, 2026, 11:27 AM UTCCVE published
2. Oct 16, 2026, 3:15 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: partial

3. Oct 19, 2026, 7:16 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in f895191dc32c53eaf443b6443fe40945b2f92287; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in cd5beda7e0e32865e214f28034bb92c1cecff885; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in eaedc0bc18be46fe7f58170e967959a932c4f824; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 07a9b32eaae792ff7d0fcac14d8920c937c0a9c3; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 8b300f726640c48c3edfe9c453334dd801f4b74e; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 5e13d0a37666955b6cfddc0f73cb40ed645b8a05; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in f6c412dcfd76b0516d51aa847d8f4c7b70381b09; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 735ee8582da3d239eb0c7a53adca61b79fb228b3

• Linux Linux

  2.6.12

• KernelLinux

  From 2.6.12 · fixed in 5.10.252; From 5.11.0 · fixed in 5.15.202; From 5.16.0 · fixed in 6.1.165; From 6.2.0 · fixed in 6.6.128; From 6.7.0 · fixed in 6.12.75; From 6.13.0 · fixed in 6.18.16; From 6.19.0 · fixed in 6.19.6

References 8