CVE-2023-53825 kcm: Fix error handling for SOCK_DGRAM in kcm_sendmsg().
A memory leak in the Linux kernel's kcm module can lead to resource exhaustion and denial of service when handling SOCK_DGRAM messages.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-53825?
CVE-2023-53825 is a memory corruption vulnerability in Linux, published on 9 Dec 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:
kcm: Fix error handling for SOCK_DGRAM in kcm_sendmsg().
syzkaller found a memory leak in kcm_sendmsg(), and commit c821a88bd720 ("kcm: Fix memory leak in error path of kcm_sendmsg()") suppressed it by updating kcm_tx_msg(head)->last_skb if partial data is copied so that the following sendmsg() will resume from the skb.
However, we cannot know how many bytes were copied when we get the error. Thus, we could mess up the MSG_MORE queue.
When kcm_sendmsg() fails for SOCK_DGRAM, we should purge the queue as we do so for UDP by udp_flush_pending_frames().
Even without this change, when the error occurred, the following sendmsg() resumed from a wrong skb and the queue was messed up. However, we have yet to get such a report, and only syzkaller stumbled on it. So, this can be changed safely.
Note this does not change SOCK_SEQPACKET behaviour.
Which versions are affected by CVE-2023-53825?
How do I fix CVE-2023-53825?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2023-53825 being exploited?
There is no known exploitation of CVE-2023-53825 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2023-53825, DEBIAN-CVE-2023-53825, GHSA-qqwx-6fr4-mfj2, UBUNTU-CVE-2023-53825.