Missing permission check in thr_kill2(2)

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Summary

CVECVE-2026-45256
StatePUBLISHED
Assignerfreebsd
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-26 15:16:39 UTC
Updated2026-06-26 18:58:48 UTC
DescriptionWhen used to deliver a signal to a specific thread, thr_kill2(2) called p_cansignal() to determine whether the operation was permitted but did not check the result before delivering the signal. The signal was sent even when the permission check failed. The system call returned the resulting error to the caller, but by then the signal had already been delivered. The missing check allows an unprivileged local user who knows or can guess a target's process and thread IDs to send any signal to a process they would not normally be permitted to signal, including processes owned by other users or by root. The same check enforces jail boundaries, so a jailed process can signal processes on the host or in other jails. Thread IDs are allocated globally and sequentially, and so can be discovered by brute force with no visibility into the target. An attacker can stop or terminate arbitrary processes, including critical system daemons, resulting in a Denial of Service (DoS).

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from ADP

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-269 | CWE-269 CWE-269 Improper Privilege Management

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Freebsd Freebsd 14.3 - All All
Operating System Freebsd Freebsd 14.3 p1 All All
Operating System Freebsd Freebsd 14.3 p10 All All
Operating System Freebsd Freebsd 14.3 p11 All All
Operating System Freebsd Freebsd 14.3 p12 All All
Operating System Freebsd Freebsd 14.3 p13 All All
Operating System Freebsd Freebsd 14.3 p14 All All
Operating System Freebsd Freebsd 14.3 p2 All All
Operating System Freebsd Freebsd 14.3 p3 All All
Operating System Freebsd Freebsd 14.3 p4 All All
Operating System Freebsd Freebsd 14.3 p5 All All
Operating System Freebsd Freebsd 14.3 p6 All All
Operating System Freebsd Freebsd 14.3 p7 All All
Operating System Freebsd Freebsd 14.3 p8 All All
Operating System Freebsd Freebsd 14.3 p9 All All
Operating System Freebsd Freebsd 14.4 - All All
Operating System Freebsd Freebsd 14.4 p1 All All
Operating System Freebsd Freebsd 14.4 p2 All All
Operating System Freebsd Freebsd 14.4 p3 All All
Operating System Freebsd Freebsd 14.4 p4 All All
Operating System Freebsd Freebsd 14.4 p5 All All
Operating System Freebsd Freebsd 14.4 rc1 All All
Operating System Freebsd Freebsd 15.0 - All All
Operating System Freebsd Freebsd 15.0 p1 All All
Operating System Freebsd Freebsd 15.0 p2 All All
Operating System Freebsd Freebsd 15.0 p3 All All
Operating System Freebsd Freebsd 15.0 p4 All All
Operating System Freebsd Freebsd 15.0 p5 All All
Operating System Freebsd Freebsd 15.0 p6 All All
Operating System Freebsd Freebsd 15.0 p7 All All
Operating System Freebsd Freebsd 15.0 p8 All All
Operating System Freebsd Freebsd 15.0 p9 All All
Operating System Freebsd Freebsd 15.1 rc2 All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA FreeBSD FreeBSD affected 15.0-RELEASE p10 release Not specified
CNA FreeBSD FreeBSD affected 14.4-RELEASE p6 release Not specified
CNA FreeBSD FreeBSD affected 14.3-RELEASE p15 release Not specified

References

ReferenceSourceLinkTags
security.freebsd.org/advisories/FreeBSD-SA-26:25.thr.asc [email protected] security.freebsd.org Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Yuxiang Yang, Yizhou Zhao, Ao Wang, Xuewei Feng, Qi Li, and Ke Xu from Tsinghua University using GLM-5.1 from Z.ai (en)

CNA: Igor Gabriel Sousa e Souza (en)

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