CVE-2026-58100 is a vulnerability in FreeBSD
Published on October 15, 2026
Memory safety bugs in kqueue copy-on-fork implementation
kqueue_fork_copy_knote() indexed into the child's file descriptor table using a knote's file descriptor number without a bounds check. Because the child's table is copied before knotes are transferred, a concurrent thread in the parent could grow the parent's table and register knotes with file descriptor numbers beyond the end of the child's table, causing an out-of-bounds read.
An unprivileged local user may be able to exploit these races to escalate privileges.
Weakness Types
What is a Race Condition Vulnerability?
The program contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.
CVE-2026-58100 has been classified to as a Race Condition vulnerability or weakness.
Out-of-bounds Read
The software reads data past the end, or before the beginning, of the intended buffer. Typically, this can allow attackers to read sensitive information from other memory locations or cause a crash. A crash can occur when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string. The expected sentinel might not be located in the out-of-bounds memory, causing excessive data to be read, leading to a segmentation fault or a buffer overflow. The software may modify an index or perform pointer arithmetic that references a memory location that is outside of the boundaries of the buffer. A subsequent read operation then produces undefined or unexpected results.
Products Associated with CVE-2026-58100
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Affected Versions
FreeBSD:- Version 15.1-RELEASE and below p4 is affected.