CVE-2025-38566 sunrpc: fix handling of server side tls alerts
A flaw in Linux kernel NFS over TLS handling allows attackers to cause a denial of service by triggering improper TLS alert processing.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-38566?
CVE-2025-38566 is a critical denial of service vulnerability in Linux kernel, published on 19 Aug 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:
sunrpc: fix handling of server side tls alerts
Scott Mayhew discovered a security exploit in NFS over TLS in tls_alert_recv() due to its assumption it can read data from the msg iterator's kvec..
kTLS implementation splits TLS non-data record payload between the control message buffer (which includes the type such as TLS aler or TLS cipher change) and the rest of the payload (say TLS alert's level/description) which goes into the msg payload buffer.
This patch proposes to rework how control messages are setup and used by sock_recvmsg().
If no control message structure is setup, kTLS layer will read and process TLS data record types. As soon as it encounters a TLS control message, it would return an error. At that point, NFS can setup a kvec backed msg buffer and read in the control message such as a TLS alert. Msg iterator can advance the kvec pointer as a part of the copy process thus we need to revert the iterator before calling into the tls_alert_recv.
Weakness: CWE-754
Which versions are affected by CVE-2025-38566?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-38566?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-38566 being exploited?
There is no known exploitation of CVE-2025-38566 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-66485, BELL-CVE-2025-38566, DEBIAN-CVE-2025-38566, GHSA-64hp-5254-q6pc, ROOT-OS-DEBIAN-13-CVE-2025-38566, ROOT-OS-UBUNTU-2404-CVE-2025-38566 and 1 more.