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

What is CVE-2026-31640?

CVE-2026-31640 is a high-severity vulnerability in Linux kernel, published on 24 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-401

Which versions are affected by CVE-2026-31640?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-31640?

Apply the vendor's patch.

Is CVE-2026-31640 being exploited?

There is no known exploitation of CVE-2026-31640 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2026-31640, DEBIAN-CVE-2026-31640, GHSA-gwvh-rgq7-hjcw, UBUNTU-CVE-2026-31640.