Security readout for executives and security teams
Plain-English summary
CVE-2021-30501 is a denial-of-service issue in UPX 4.0. A specially crafted file can trigger an assertion abort in UPX memory allocation handling, causing the UPX process to stop. The sources do not show system compromise, data theft, or active exploitation.
Executive priority
Treat this as a targeted operational availability risk, not a broad compromise risk. Prioritize remediation if UPX is used in automated services that handle external files, because a crash could disrupt analysis or processing pipelines.
Technical view
The issue is reported in UPX MemBuffer::alloc() in mem.cpp and classified as input validation weakness CWE-20. Processing a crafted file can reach an assertion abort path, terminating the process. Public references include an upstream issue, pull request, and commit, but no CVSS score or fixed release version is provided in the bundle.
Likely exposure
Exposure is most likely where UPX 4.0 processes untrusted or attacker-supplied packed files, such as automated file analysis, build tooling, or security scanning workflows. Systems that do not run UPX against external files are unlikely to be materially exposed.
Exploitation context
The available sources describe a crafted-file denial of service. The CVE is not listed as CISA KEV in the bundle, and no cited source here supports active exploitation in the wild.
Researcher notes
Evidence is narrow but consistent: the CVE description, upstream issue, pull request, and commit point to an assertion abort in MemBuffer::alloc(). The bundle lacks CVSS, exploit prevalence, and a named fixed release, so exposure assessment depends on local UPX usage.
Mitigation direction
- Identify environments running UPX 4.0 or packages based on it.
- Check upstream UPX and distributor guidance for fixed builds.
- Review the referenced pull request and commit before accepting patched packages.
- Avoid processing untrusted files with affected UPX builds where feasible.
- Isolate automated UPX file-processing workflows from critical services.
Validation and detection
- Inventory UPX versions in developer, CI, and file-analysis environments.
- Confirm whether UPX processes untrusted or externally supplied files.
- Check package changelogs against the referenced upstream commit.
- Verify updated builds no longer contain the vulnerable code path.
- Review crash logs for UPX assertion aborts during file processing.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-20: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-30501 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.redhat.com/show_bug.cgi?id=1948696CVE reference · x_refsource_MISC
- https://github.com/upx/upx/issues/486CVE reference · x_refsource_MISC
- https://github.com/upx/upx/pull/487CVE reference · x_refsource_MISC
- https://github.com/upx/upx/commit/28e761cd42211dfe0124b7a29b2f74730f453e46CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.