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Fencer Vulns
high 7.5

CVE-2026-31640 json

rxrpc: Fix use of wrong skb when comparing queued RESP challenge serial

published 2026-04-24 6 mo ago modified 2026-08-05 3 mo ago also EUVD-2026-25533

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 37%
public exploits
0
none known

Summary

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.

Patch / fix

  • Linux Linux 6.18.23, 6.19.13, 7.0
  • linux Debian 14 6.19.13-1

debian advisories DEBIAN-CVE-2026-31640

  • linux-nvidia Ubuntu 26.04 LTS 7.0.0-1006.6

ubuntu advisories UBUNTU-CVE-2026-31640

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-31640 updated cvss 5.5

kernel: rxrpc: Fix use of wrong skb when comparing queued RESP challenge serial

  • Red Hat Enterprise Linux 10 kernel
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.43% chance of exploitation in the next 30 days, higher than 37% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-401 Missing Release of Memory after Effective Lifetime
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.