SB2026082640 - Unauthorized credential switching in FreeBSD

Description

This security bulletin contains information about 1 vulnerability.

1) Improper privilege management (CVE-ID: CVE-2026-58092)

CWE-ID: CWE-269 - Improper Privilege Management

CVSSv4: 5.7 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a local user to escalate privileges.

The vulnerability exists due to improper handling of primary group identification in group_is_primary() in the mac_do policy module when applying credential transition rules that do not explicitly specify a target group. A local user can trigger a crafted credential switch to set an unintended primary group ID to escalate privileges.

Exploitation requires a mac_do ruleset that applies to the calling process, and setting the primary group ID to 0 requires the process to have an empty supplementary group list.

Remediation

Install update from vendor's website.

References

• https://www.freebsd.org/security/advisories/FreeBSD-SA-26:59.mac_do.asc
• https://cgit.freebsd.org/src/commit/?id=ae27dff4710b