What’s Vulnerable › Vulnerabilities

CVE-2025-37879: 9p/net: fix improper handling of bogus negative read/write replies

• Severity: high (CVSS 7.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-05-09 · updated 2026-07-30
• Weakness: CWE-125

Description

In the Linux kernel, the following vulnerability has been resolved: 9p/net: fix improper handling of bogus negative read/write replies In p9_client_write() and p9_client_read_once(), if the server incorrectly replies with success but a negative write/read count then we would consider written (negative) <= rsize (positive) because both variables were signed. Make variables unsigned to avoid this problem. The reproducer linked below now fails with the following error instead of a null pointer deref: 9pnet: bogus RWRITE count (4294967295 > 3)

Affected products

• Debian Linux: 11.0
• Linux kernel: before 6.1.136; from 6.2 before 6.6.89; from 6.7 before 6.12.26; from 6.13 before 6.14.5 — fixed in 6.1.136, 6.12.26, 6.14.5, 6.6.89

How to fix

Upgrade to a fixed version: Linux kernel 6.1.136, 6.12.26, 6.14.5, 6.6.89. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/374e4cd75617c8c2552f562f39dd989583f5c330
• https://git.kernel.org/stable/c/468ff4a7c61fb811c596a7c44b6a5455e40fd12b
• https://git.kernel.org/stable/c/a68768e280b7d0c967ea509e791bb9b90adc94a5
• https://git.kernel.org/stable/c/c548f95688e2b5ae0e2ae43d53cf717156c7d034
• https://git.kernel.org/stable/c/d0259a856afca31d699b706ed5e2adf11086c73b
• https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html

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