FreeBSD Jail nullfs FD Exchange Exploit Bypass Jail Root
CVE-2025-15576 Published on March 9, 2026
Jail chroot escape via fd exchange with a different jail
If two sibling jails are restricted to separate filesystem trees, which is to say that neither of the two jail root directories is an ancestor of the other, jailed processes may nonetheless be able to access a shared directory via a nullfs mount, if the administrator has configured one.
In this case, cooperating processes in the two jails may establish a connection using a unix domain socket and exchange directory descriptors with each other.
When performing a filesystem name lookup, at each step of the lookup, the kernel checks whether the lookup would descend below the jail root of the current process. If the jail root directory is not encountered, the lookup continues.
In a configuration where processes in two different jails are able to exchange file descriptors using a unix domain socket, it is possible for a jailed process to receive a directory for a descriptor that is below that process' jail root. This enables full filesystem access for a jailed process, breaking the chroot.
Note that the system administrator is still responsible for ensuring that an unprivileged user on the jail host is not able to pass directory descriptors to a jailed process, even in a patched kernel.
Vulnerability Analysis
CVE-2025-15576 is exploitable with local system access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and no impact on availability.
Weakness Types
Improper Privilege Management
The software does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.
Exposure of Data Element to Wrong Session
The product does not sufficiently enforce boundaries between the states of different sessions, causing data to be provided to, or used by, the wrong session.
Improper Filtering of Special Elements
The software receives data from an upstream component, but does not filter or incorrectly filters special elements before sending it to a downstream component.
Products Associated with CVE-2025-15576
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Affected Versions
FreeBSD:- Version 14.3-RELEASE and below p9 is affected.
- Version 13.5-RELEASE and below p10 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.