FreeBSD Kernel: Page Size Race in FIOSSHMLPGCNF ioctl
CVE-2026-58094 Published on August 26, 2026
TOCTOU race in POSIX shared memory large page configuration
The FIOSSHMLPGCNF ioctl(2) operation configures the page size for a largepage shared memory object. This is intended to be used immediately after creating the object, before any memory is allocated for the object. The handler checked whether a page size had already been configured without holding the rangelock. Two concurrent callers could both observe an unconfigured object and set conflicting page sizes, leaving the object in an inconsistent state.
An unprivileged local user can exploit this race to escalate privileges.
Vulnerability Analysis
CVE-2026-58094 is exploitable with local system access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.
Weakness Type
What is a TOCTTOU Vulnerability?
The software checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the software to perform invalid actions when the resource is in an unexpected state. This weakness can be security-relevant when an attacker can influence the state of the resource between check and use. This can happen with shared resources such as files, memory, or even variables in multithreaded programs.
CVE-2026-58094 has been classified to as a TOCTTOU vulnerability or weakness.
Products Associated with CVE-2026-58094
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Affected Versions
FreeBSD:- Version 15.1-RELEASE and below p3 is affected.
- Version 15.0-RELEASE and below p13 is affected.
- Version 14.4-RELEASE and below p9 is affected.