CVE-2021-23240

Privilege escalation via sudoedit temporary-file symlink race

Published Jan 12, 2021 · Updated Aug 3, 2024

A symlink race in Sudo before 1.9.5 allows local users to take ownership of arbitrary files through SELinux-enabled sudoedit. selinux_edit_copy_tfiles calls chown() on a user-controlled temporary path after the user can replace the file with a symlink. Exploitation requires sudoedit permission, SELinux support in permissive mode or an unconfined domain, and disabled protected-symlink enforcement; changed ownership enables privilege escalation.

CVSS severity7.8
High
EPSS probability1.07%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

A symlink race in Sudo before 1.9.5 allows local users to take ownership of arbitrary files through SELinux-enabled sudoedit. selinux_edit_copy_tfiles calls chown() on a user-controlled temporary path after the user can replace the file with a symlink. Exploitation requires sudoedit permission, SELinux support in permissive mode or an unconfined domain, and disabled protected-symlink enforcement; changed ownership enables privilege escalation.

The record

CVE
CVE-2021-23240
Published
Jan 12, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-367, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 12, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8UbuntuCVSS:3.1/AV:L/AC:L/PR:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo