CVE-2025-39800

A flaw was found in the Linux kernel's btrfs filesystem. A local user could exploit this vulnerability when the system processes an unexpected generation for an extent buffer during a root copy operation. Instead of properly stopping the transaction, the system allows corrupted metadata to persist. This issue can lead to a denial of service (DoS), making the system or data unavailable.

A flaw was found in the Linux kernel's btrfs filesystem. Red Hat rates this flaw as having Moderate security impact (CVSS 5.5, AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H). When the btrfs code clones a tree root at btrfs_copy_root() and encounters an extent buffer with an unexpected generation, it previously only issued a WARN_ON and continued the transaction instead of aborting it, allowing metadata with an unexpected generation to be persisted. A local user able to trigger a root copy operation on a btrfs filesystem could use this flaw to persist corrupted metadata, resulting in a denial of service. This issue affects the kernel and kernel-rt packages in Red Hat Enterprise Linux 7 Extended Lifecycle Support, where the fix has been deferred: RHEL 7 is in the extended support phase and this moderate-severity, local, availability-only flaw falls below the fix threshold for that phase, so the residual risk of a local denial of service remains until a fix is delivered. Red Hat Enterprise Linux 6 is out of support scope, and Red Hat Enterprise Linux 8, 9, and 10 and Red Hat In-Vehicle OS are not affected because the vulnerable code is not present in those streams. Red Hat's Moderate rating is lower than the upstream CVE.org severity of Important (CVSS 7.8) because Red Hat's assessment finds the impact limited to availability, with no confidentiality or integrity impact.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.