CVE-2025-39823 KVM: x86: use array_index_nospec with indices that come from guest
Guest-controlled indices in KVM x86 lacked speculative execution clamping, potentially allowing side-channel data disclosure.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-39823?
CVE-2025-39823 is a high-severity vulnerability in Debian Debian Linux, published on 16 Sep 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
KVM: x86: use array_index_nospec with indices that come from guest
min and dest_id are guest-controlled indices. Using array_index_nospec() after the bounds checks clamps these values to mitigate speculative execution side-channels.
Weakness: CWE-129
Which versions are affected by CVE-2025-39823?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2025-39823?
Apply the vendor's patch.
Is CVE-2025-39823 being exploited?
There is no known exploitation of CVE-2025-39823 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as AZL-67419, AZL-74718, BELL-CVE-2025-39823, DEBIAN-CVE-2025-39823, GHSA-g6f5-85j8-c4fr, ROOT-OS-DEBIAN-11-CVE-2025-39823 and 5 more.