CVE-2026-31640: rxrpc: Fix use of wrong skb when comparing queued RESP challenge serial

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-24 · updated 2026-06-17
Weakness: CWE-401

Description

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix use of wrong skb when comparing queued RESP challenge serial In rxrpc_post_response(), the code should be comparing the challenge serial number from the cached response before deciding to switch to a newer response, but looks at the newer packet private data instead, rendering the comparison always false. Fix this by switching to look at the older packet. Fix further[1] to substitute the new packet in place of the old one if newer and also to release whichever we don't use.

Affected products

Linux kernel: from 6.16.1 before 6.18.23; from 6.19 before 6.19.13; 6.16, 7.0-rc1, 7.0-rc2, 7.0-rc3, 7.0-rc4, 7.0-rc5 (+2) — fixed in 6.18.23, 6.19.13

How to fix

Upgrade to a fixed version: Linux kernel 6.18.23, 6.19.13. Check the vendor advisory for mitigations.

References

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