CVE-2021-43314Public exploitNetwork attack vector

Process crash via unchecked ELF hash-table access

Published Mar 24, 2023 · Updated Feb 25, 2025

Heap-based buffer overflow in UPX before 4.0.0-git-c6b9e3c62d15 allows remote attackers to crash the process via crafted ELF data. PackLinuxElf32::elf_lookup() derives a hash-table index from untrusted ELF metadata and passes an out-of-range pointer to get_le32() without validating the referenced range. Processing the crafted ELF is required; the observed segmentation fault terminates UPX, with no reported data disclosure or modification.

CVSS severity7.5
High
EPSS probability0.82%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Heap-based buffer overflow in UPX before 4.0.0-git-c6b9e3c62d15 allows remote attackers to crash the process via crafted ELF data. PackLinuxElf32::elf_lookup() derives a hash-table index from untrusted ELF metadata and passes an out-of-range pointer to get_le32() without validating the referenced range. Processing the crafted ELF is required; the observed segmentation fault terminates UPX, with no reported data disclosure or modification.

The record

CVE
CVE-2021-43314
Published
Mar 24, 2023
Updated
Feb 25, 2025
Vendor
The UPX Team
Product
UPX
Classifications
CWE-119, CWE-787
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 24, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 25, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=upx before 4.0.0-git-c6b9e3c62d15

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The UPX Team · UPXversion=upx before 4.0.0-git-c6b9e3c62d15

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-787Out-of-bounds Write

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo