Bug 2461545 (CVE-2026-31630)

Summary: CVE-2026-31630 kernel: rxrpc: proc: size address buffers for %pISpc output
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel, specifically within the rxrpc component. The AF_RXRPC procfs helpers use fixed-size buffers to format local and remote socket addresses. When processing certain IPv6 addresses with ports, the formatted string can exceed the buffer's capacity, leading to a buffer overflow. This memory corruption vulnerability can cause system instability or a denial of service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-04-24 15:07:42 UTC 
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
Comment 1 Keith Grant 2026-04-24 20:45:53 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026042453-CVE-2026-31630-4218@gregkh/T