CVE-2026-31681

In the Linux kernel, the following vulnerability has been resolved: netfilter: xt_multiport: validate range encoding in checkentry ports_match_v1() treats any non-zero pflags entry as the start of a port range and unconditionally consumes the next ports[] element as the range end. The checkentry path currently validates protocol, flags and count, but it does not validate the range encoding itself. As a result, malformed rules can mark the last slot as a range start or place two range starts back to back, leaving ports_match_v1() to step past the last valid ports[] element while interpreting the rule. Reject malformed multiport v1 rules in checkentry by validating that each range start has a following element and that the following element is not itself marked as another range start.

CVSS 3.1

5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS

0.1% chance of exploitation in the next 30 days; higher than 2% of CVEs (scores of 2026-10-25)

Published

2026-04-25

Modified

2026-10-15

Record from

the NVD, synced 2026-10-19

Affected

• linux:linux_kernel

References

• https://git.kernel.org/stable/c/1e4baa853f1cc4227e04f52d6860524707cfb294
• https://git.kernel.org/stable/c/36bf0d98e180a7c384c8d8a59b0d2d4b80e5eb16
• https://git.kernel.org/stable/c/8368ce8eb01f0b91111d814703696e780d0ef12f
• https://git.kernel.org/stable/c/8c5bf8f5b478f569191c4a7982de7cd5f5f73c1a
• https://git.kernel.org/stable/c/aec14808271f2bf2b656de6ff12dfe73c5fd3b67

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