Linux Kernel up to 6.18.22/6.19.12 rxrpc lib/vsprintf.c ipv6_addr_is_isatap stack-based overflow

Summaryinfo

A vulnerability marked as critical has been reported in Linux Kernel up to 6.18.22/6.19.12. The affected element is the function ipv6_addr_is_isatap in the library lib/vsprintf.c of the component rxrpc. Performing a manipulation results in stack-based overflow. This vulnerability is known as CVE-2026-31630. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.18.22/6.19.12. It has been classified as critical. This affects the function ipv6_addr_is_isatap in the library lib/vsprintf.c of the component rxrpc. The manipulation with an unknown input leads to a stack-based overflow vulnerability. CWE is classifying the issue as CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-31630 since 03/09/2026. The exploitability is told to be easy. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/04/2026).

The vulnerability scanner Nessus provides a plugin with the ID 310516 (Linux Distros Unpatched Vulnerability : CVE-2026-31630), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.18.23 or 6.19.13 eliminates this vulnerability. Applying the patch db297c78ce537c9ac96f0eda9b25ad72c8caefa9/10ebed83f9f6414af4e85bc85ffaeda7effdd874/a44ce6aa2efb61fe44f2cfab72bb01544bbca272 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (310516) and CERT Bund (WID-SEC-2026-1279). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Google Container-Optimized OS
• Debian Linux
• Red Hat Enterprise Linux
• Oracle Linux
• Open Source Linux Kernel

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.18.14
• 6.18.15
• 6.18.16
• 6.18.17
• 6.18.18
• 6.18.19
• 6.18.20
• 6.18.21
• 6.18.22
• 6.19.0
• 6.19.1
• 6.19.2
• 6.19.3
• 6.19.4
• 6.19.5
• 6.19.6
• 6.19.7
• 6.19.8
• 6.19.9
• 6.19.10
• 6.19.11
• 6.19.12

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Entryinfo

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