CVE-2021-3899

Local root code execution via executable-replacement race

Published Jun 3, 2024 · Updated Aug 19, 2024

A race condition in Apport before 2.21.0 allows local users to execute arbitrary code as root during crash processing. The replaced-executable check performs time-of-check/time-of-use validation that can be raced after a process crashes, causing Apport to accept attacker-controlled executable state. Successful exploitation requires local access and the correct local configuration, and it grants root-level code execution without user interaction.

CVSS severity7.8
High
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A race condition in Apport before 2.21.0 allows local users to execute arbitrary code as root during crash processing. The replaced-executable check performs time-of-check/time-of-use validation that can be raced after a process crashes, causing Apport to accept attacker-controlled executable state. Successful exploitation requires local access and the correct local configuration, and it grants root-level code execution without user interaction.

The record

CVE
CVE-2021-3899
Published
Jun 3, 2024
Updated
Aug 19, 2024
Vendor
Canonical
Product
Apport
Classifications
CWE-367, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 3, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 2024Record 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 <2.21.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Canonical · Apportversion=0 <2.21.0

Published CVSS scores

7.8CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8NVDCVSS: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

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Your stack

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