HOMEVULNERABILITIESCVE-2021-20285
MEDIUM

CVE-2021-20285

CWE-119Published: March 26, 2021· Updated: Jun 17, 2026

6.6
CVSS v3.1

Official Description

A flaw was found in upx canPack in p_lx_elf.cpp in UPX 3.96. This flaw allows attackers to cause a denial of service (SEGV or buffer overflow and application crash) or possibly have unspecified other impacts via a crafted ELF. The highest threat from this vulnerability is to system availability.

NVD Source

Technical Analysis

CVE-2021-20285 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 6.6.

From a weakness classification perspective (CWE-119): Buffer overflow vulnerabilities can lead to arbitrary code execution or denial of service by corrupting adjacent memory.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorLocal
Attack ComplexityLow
Privileges Req.None
User InteractionRequired
ScopeUnchanged
Impact
ConfidentialityLow
IntegrityLow
AvailabilityHigh
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H

Affected Vendors & Products

upx1 product(s)
upx
Source: NVD CPE · 1 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://bugzilla.redhat.com/show_bug.cgi?id=1937787
ADVISORYhttps://github.com/upx/upx/issues/421
ADVISORYhttps://bugzilla.redhat.com/show_bug.cgi?id=1937787
ADVISORYhttps://github.com/upx/upx/issues/421

All References (4)

→
https://bugzilla.redhat.com/show_bug.cgi?id=1937787Issue Tracking · Third Party Advisory
→
https://github.com/upx/upx/issues/421Exploit · Issue Tracking · Third Party Advisory
→
https://bugzilla.redhat.com/show_bug.cgi?id=1937787Issue Tracking · Third Party Advisory
→
https://github.com/upx/upx/issues/421Exploit · Issue Tracking · Third Party Advisory

Quick Facts

CVE IDCVE-2021-20285
CVSS Score6.6 / 10
SeverityMEDIUM
WeaknessCWE-119
CISA KEVNo
Affected1 vendor(s)
PublishedMar 26, 2021

Related CVEs (CWE-119)

CVE-2014-0556
10.0
CVE-2014-0515
10.0
CVE-2011-2595
10.0
CVE-2008-1602
10.0
CVE-2011-1567
10.0
CVE-2009-3958
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-20285 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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