CVE-2025-37879 9p/net: fix improper handling of bogus negative read/write replies
A signed integer comparison flaw in the Linux kernel 9p network client allows a malicious server to trigger a null pointer dereference, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-37879?
CVE-2025-37879 is a critical vulnerability in Debian Debian Linux, published on 9 May 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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)
Weakness: CWE-125
Which versions are affected by CVE-2025-37879?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2025-37879?
Apply the vendor's patch.
Is CVE-2025-37879 being exploited?
There is no known exploitation of CVE-2025-37879 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as AZL-70153, BELL-CVE-2025-37879, DEBIAN-CVE-2025-37879, GHSA-9hq9-gv35-c42w, ROOT-OS-DEBIAN-11-CVE-2025-37879, ROOT-OS-DEBIAN-12-CVE-2025-37879 and 3 more.