# CVE-2026-31630

> Vulnerability · severity: **HIGH** (CVSS 7.8).

## Description

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

## Key facts

- **CVE ID:** CVE-2026-31630
- **Published:** 2026-04-24
- **CVSS severity:** HIGH
- **CVSS base score:** 7.8
- **CWE codes:** NVD-CWE-noinfo

## Affected products

- `linux:linux_kernel`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31630

## Citation

> AI Analytics. CVE-2026-31630. Retrieved 2026-08-02 from https://api.ai-analytics.org/cve/CVE-2026-31630. Derived from NIST NVD. Licensed CC0.

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