CVE-2021-3899

HIGHNVD 7.87.8—Elevated

7.8

There is a race condition in the 'replaced executable' detection that, with the correct local configuration, allow an attacker to execute arbitrary code as root.

CVSS v3: 7.8
EG Score: 7.8(medium)
EPSS: 84.9%
KEV: Not listed

Published

June 3, 2024

Last Modified

August 26, 2025

References (6)

security@ubuntuhttps://bugs.launchpad.net/ubuntu/+source/apport/+bug/1948376
security@ubuntuhttps://ubuntu.com/security/notices/USN-5427-1
security@ubuntuhttps://www.cve.org/CVERecord?id=CVE-2021-3899
af854a3a-2127-422b-91ae-364da2661108https://bugs.launchpad.net/ubuntu/+source/apport/+bug/1948376
af854a3a-2127-422b-91ae-364da2661108https://ubuntu.com/security/notices/USN-5427-1
af854a3a-2127-422b-91ae-364da2661108https://www.cve.org/CVERecord?id=CVE-2021-3899

Patch Availability(2)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
ubuntu	python3-problem-report (2.20.1-0ubuntu2.30+esm4) @ xenial	2026-05-24	ubuntu
ubuntu	apport-noui (2.20.11-0ubuntu82.1) @ jammy	2026-05-24	ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

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

All Vendor Advisories

(2)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 11× in last 7d / 20× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-06-02 20:11 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-29 13:42 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-24 00:38 UTCEG score recompute
2026-05-24 00:38 UTCVendor advisory

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 GitHub PoC). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

GitHub PoCliumuqing/CVE-2021-3899_PoC
First seen May 21, 2022
race condition in apport lead to Local Privilege Escalation on Ubuntu
Open source ↗

Frequently asked(5)

What is CVE-2021-3899?

CVE-2021-3899 is a high vulnerability published on June 3, 2024. There is a race condition in the 'replaced executable' detection that, with the correct local configuration, allow an attacker to execute arbitrary code as root.

When was CVE-2021-3899 disclosed?

CVE-2021-3899 was first published in the National Vulnerability Database on June 3, 2024, with the most recent update on August 26, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-3899 actively exploited?

CVE-2021-3899 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 84.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-3899?

CVE-2021-3899 has a CVSS v3 base score of 7.8 (NVD).

How do I remediate CVE-2021-3899?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-3899, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-3899

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