CVE-2026-57589

Local root escalation via semaphore use-after-free

Published Jun 25, 2026 · Updated Jun 25, 2026

Use-after-free in OpenBSD through 7.9 allows local users to escalate privileges to root through the System V semaphore subsystem. The kernel keeps using a semaphore object after tsleep in sys_semget() without retaining a reference, so another context can free it during the switch. Exploitation requires local syscall access and winning this race; success grants root-level control of the affected system.

CVSS severity7.8
High
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in OpenBSD through 7.9 allows local users to escalate privileges to root through the System V semaphore subsystem. The kernel keeps using a semaphore object after tsleep in sys_semget() without retaining a reference, so another context can free it during the switch. Exploitation requires local syscall access and winning this race; success grants root-level control of the affected system.

The record

CVE
CVE-2026-57589
Published
Jun 25, 2026
Updated
Jun 25, 2026
Vendor
OpenBSD Project
Product
OpenBSD
Classifications
CWE-416, T1068
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=7.9

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

OpenBSD Project · OpenBSDversion=0 <=7.9

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.4MITRECVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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