CVE-2025-40046 io_uring/zcrx: fix overshooting recv limit
A double accounting bug in the Linux kernel's io_uring zero-copy receive path causes an integer underflow, potentially leading to 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-2025-40046?
CVE-2025-40046 is a high-severity vulnerability in Linux, published on 28 Oct 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:
io_uring/zcrx: fix overshooting recv limit
It's reported that sometimes a zcrx request can receive more than was requested. It's caused by io_zcrx_recv_skb() adjusting desc->count for all received buffers including frag lists, but then doing recursive calls to process frag list skbs, which leads to desc->count double accounting and underflow.
Which versions are affected by CVE-2025-40046?
How do I fix CVE-2025-40046?
Apply the vendor's patch.
Is CVE-2025-40046 being exploited?
There is no known exploitation of CVE-2025-40046 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40046, DEBIAN-CVE-2025-40046, GHSA-f89g-f269-w35c, UBUNTU-CVE-2025-40046.