CVE-2025-39790 bus: mhi: host: Detect events pointing to unexpected TREs
A race condition in the Linux kernel MHI host driver allows double-freeing buffers, potentially leading to code execution or system crashes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-39790?
CVE-2025-39790 is a high-severity use after free vulnerability in Debian Debian Linux, published on 11 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:
bus: mhi: host: Detect events pointing to unexpected TREs
When a remote device sends a completion event to the host, it contains a pointer to the consumed TRE. The host uses this pointer to process all of the TREs between it and the host's local copy of the ring's read pointer. This works when processing completion for chained transactions, but can lead to nasty results if the device sends an event for a single-element transaction with a read pointer that is multiple elements ahead of the host's read pointer.
For instance, if the host accesses an event ring while the device is updating it, the pointer inside of the event might still point to an old TRE. If the host uses the channel's xfer_cb() to directly free the buffer pointed to by the TRE, the buffer will be double-freed.
This behavior was observed on an ep that used upstream EP stack without 'commit 6f18d174b73d ("bus: mhi: ep: Update read pointer only after buffer is written")'. Where the device updated the events ring pointer before updating the event contents, so it left a window where the host was able to access the stale data the event pointed to, before the device had the chance to update them. The usual pattern was that the host received an event pointing to a TRE that is not immediately after the last processed one, so it got treated as if it was a chained transaction, processing all of the TREs in between the two read pointers.
This commit aims to harden the host by ensuring transactions where the event points to a TRE that isn't local_rp + 1 are chained.
[mani: added stable tag and reworded commit message]
Weakness: CWE-415
Which versions are affected by CVE-2025-39790?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2025-39790?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2025-39790 being exploited?
There is no known exploitation of CVE-2025-39790 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as BELL-CVE-2025-39790, DEBIAN-CVE-2025-39790, GHSA-q63v-r8x9-2c5r, ROOT-OS-DEBIAN-11-CVE-2025-39790, ROOT-OS-DEBIAN-12-CVE-2025-39790, ROOT-OS-DEBIAN-13-CVE-2025-39790 and 3 more.