CVE-2025-39717: open_tree_attr: do not allow id-mapping changes without OPEN_TREE_CLONE
In the Linux kernel, the following vulnerability has been resolved:
opentreeattr: do not allow id-mapping changes without OPENTREECLONE
As described in commit 7a54947e727b ('Merge patch series "fs: allow changing idmappings"'), opentreeattr(2) was necessary in order to allow for a detached mount to be created and have its idmappings changed without the risk of any racing threads operating on it. For this reason, mountsetattr(2) still does not allow for id-mappings to be changed.
However, there was a bug in commit 2462651ffa76 ("fs: allow changing idmappings") which allowed users to bypass this restriction by calling opentreeattr(2) without OPENTREECLONE.
canidmapmount() prevented this bug from allowing an attached mountpoint's id-mapping from being modified (thanks to an isanonns() check), but this still allows for detached (but visible) mounts to have their be id-mapping changed. This risks the same UAF and locking issues as described in the merge commit, and was likely unintentional.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2025-39717?
CVE-2025-39717 has been classified as a moderate severity vulnerability.
How do I fix CVE-2025-39717?
To fix CVE-2025-39717, ensure you are running an updated version of the Linux kernel where the vulnerability has been patched.
What does CVE-2025-39717 affect?
CVE-2025-39717 affects the Linux kernel, specifically the open_tree_attr function.
What type of vulnerability is CVE-2025-39717?
CVE-2025-39717 is a security vulnerability that involves improper handling of id-mapping changes.
Can CVE-2025-39717 be exploited remotely?
CVE-2025-39717 primarily poses a risk in environments where id-mapping changes are used, potentially allowing local exploitation.