CVE-2021-43315Public exploitNetwork attack vector

Process crash via unchecked ELF hash indexes

Published Mar 24, 2023 · Updated Feb 25, 2025

Heap-based buffer overflow in UPX before 4.0.0-git-c6b9e3c62d15 allows attackers to crash the process via a crafted ELF file. PackLinuxElf32::elf_lookup trusts attacker-controlled DT_HASH and DT_GNU_HASH table sizes and indexes, allowing get_te32 to read four bytes beyond the loaded file image. The crafted file must be processed for decompression; the demonstrated consequence is a UPX process crash rather than a system-wide interruption.

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

What happened

Heap-based buffer overflow in UPX before 4.0.0-git-c6b9e3c62d15 allows attackers to crash the process via a crafted ELF file. PackLinuxElf32::elf_lookup trusts attacker-controlled DT_HASH and DT_GNU_HASH table sizes and indexes, allowing get_te32 to read four bytes beyond the loaded file image. The crafted file must be processed for decompression; the demonstrated consequence is a UPX process crash rather than a system-wide interruption.

The record

CVE
CVE-2021-43315
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

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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.

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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

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Your stack

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