A heap-based buffer over-read was discovered in the acc_ua_get_be32 function in miniacc.h in UPX 4.0.0 via a crafted Mach-O file.

published 2022-08-25 4 y ago modified 2026-06-17 4 mo ago also EUVD-2020-20301

cvss: 7.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 25%
public exploits: 0; none known

Patch / fix

distros 2

debian alpine

upx-ucl Debian 14, Debian 13 4.2.2-1

debian advisories DEBIAN-CVE-2020-27799

upx Alpine 3.24, Alpine 3.23, Alpine 3.22 +5 more 4.0.0-r0

alpine advisories ALPINE-CVE-2020-27799

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Exploit prediction

0.33% chance of exploitation in the next 30 days, higher than 25% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/upx/upx/issues/391 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	7.8	CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

n/a upx

Classification

Weakness

CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-125 Out-of-bounds Read

References

github.com /upx/upx/issues/391
exploit, issue-tracking, third-party-advisory

Sources

CVE List CVE-2020-27799
NVD CVE-2020-27799

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary