CVE-2021-30501

MEDIUMNVD 5.55.5—

5.5

An assertion abort was found in upx MemBuffer::alloc() in mem.cpp, in version UPX 4.0.0. The flow allows attackers to cause a denial of service (abort) via a crafted file.

CVSS v3: 5.5
EG Score: 5.5(medium)
EPSS: 42.5%
KEV: Not listed

Published

May 27, 2021

Last Modified

April 11, 2025

References (8)

secalert@redhathttps://bugzilla.redhat.com/show_bug.cgi?id=1948696
secalert@redhathttps://github.com/upx/upx/commit/28e761cd42211dfe0124b7a29b2f74730f453e46
secalert@redhathttps://github.com/upx/upx/issues/486
secalert@redhathttps://github.com/upx/upx/pull/487
af854a3a-2127-422b-91ae-364da2661108https://bugzilla.redhat.com/show_bug.cgi?id=1948696
af854a3a-2127-422b-91ae-364da2661108https://github.com/upx/upx/commit/28e761cd42211dfe0124b7a29b2f74730f453e46
af854a3a-2127-422b-91ae-364da2661108https://github.com/upx/upx/issues/486
af854a3a-2127-422b-91ae-364da2661108https://github.com/upx/upx/pull/487

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 18× 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
2026-06-02 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
2026-05-29 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 16:01 UTCEG score recompute
2026-05-26 16:01 UTCGHSA enrichment
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch

Frequently asked(5)

What is CVE-2021-30501?

CVE-2021-30501 is a medium vulnerability published on May 27, 2021. An assertion abort was found in upx MemBuffer::alloc() in mem.cpp, in version UPX 4.0.0. The flow allows attackers to cause a denial of service (abort) via a crafted file.

When was CVE-2021-30501 disclosed?

CVE-2021-30501 was first published in the National Vulnerability Database on May 27, 2021, with the most recent update on April 11, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-30501 actively exploited?

CVE-2021-30501 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 42.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-30501?

CVE-2021-30501 has a CVSS v3 base score of 5.5 (NVD).

How do I remediate CVE-2021-30501?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-30501, 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

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CVE-2021-30501

📅 Published

🔄 Last Modified

🔗 References (8)

Weakness Classification(2)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-30501?

🔗 Related CVEs(same CWE)

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Published

Last Modified

References (8)

Frequently asked(5)

Related CVEs(same CWE)