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Fencer Vulns
high 7.8

CVE-2026-31630 json

rxrpc: proc: size address buffers for %pISpc output

published 2026-04-24 6 mo ago modified 2026-10-21 19 d ago also EUVD-2026-25523

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 7%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

rxrpc: proc: size address buffers for %pISpc output

The AF_RXRPC procfs helpers format local and remote socket addresses into fixed 50-byte stack buffers with "%pISpc".

That is too small for the longest current-tree IPv6-with-port form the formatter can produce. In lib/vsprintf.c, the compressed IPv6 path uses a dotted-quad tail not only for v4mapped addresses, but also for ISATAP addresses via ipv6_addr_is_isatap().

As a result, a case such as

[ffff:ffff:ffff:ffff:0:5efe:255.255.255.255]:65535

is possible with the current formatter. That is 50 visible characters, so 51 bytes including the trailing NUL, which does not fit in the existing char[50] buffers used by net/rxrpc/proc.c.

Size the buffers from the formatter's maximum textual form and switch the call sites to scnprintf().

Changes since v1: - correct the changelog to cite the actual maximum current-tree case explicitly - frame the proof around the ISATAP formatting path instead of the earlier mapped-v4 example

Patch / fix

  • Linux Linux 5.10.258, 5.15.209, 6.1.175, 6.6.160, 6.12.114, 6.18.23, 6.19.13, 7.0
  • linux Debian 12 6.1.176-1
  • linux Debian 13 6.12.115-2
  • linux Debian 14 6.19.13-1

debian advisories DEBIAN-CVE-2026-31630

  • linux Ubuntu 22.04 LTS 5.15.0-186.196
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1112.119
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1112.122
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1108.114
  • linux-ibm Ubuntu 22.04 LTS 5.15.0-1106.110
  • linux-kvm Ubuntu 22.04 LTS 5.15.0-1104.109
  • linux-azure Ubuntu 22.04 LTS 5.15.0-1117.126
  • linux-gkeop Ubuntu 22.04 LTS 5.15.0-1095.103

ubuntu advisories UBUNTU-CVE-2026-31630

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-2026-31630 updated cvss 5.5

kernel: rxrpc: proc: size address buffers for %pISpc output

  • 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 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
    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

cisa ICSA-26-295-16 updated cvss 7.8

Siemens SIMATIC S7-1500 TM MFP

  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
24 d ago

Exploit prediction

0.18% chance of exploitation in the next 30 days, higher than 7% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux
  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem

Classification

Weakness
  • CWE-121 Stack-based Buffer Overflow
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.