CVE-2021-46179Public exploitNetwork attack vector

Compressor crash via oversized read length

Published Aug 22, 2023 · Updated Oct 3, 2024

Reachable assertion in UPX before 4.0.0 allows remote attackers to crash the compressor by supplying a crafted executable file. InputFile::readx asserts that a requested read length does not exceed its MemBuffer size; a crafted Mach-O input reaches the check with an oversized length and aborts the process. Processing requires a user to run UPX against the file, and the demonstrated consequence is termination of that UPX process rather than host-wide service loss.

CVSS severity6.5
Medium
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reachable assertion in UPX before 4.0.0 allows remote attackers to crash the compressor by supplying a crafted executable file. InputFile::readx asserts that a requested read length does not exceed its MemBuffer size; a crafted Mach-O input reaches the check with an oversized length and aborts the process. Processing requires a user to run UPX against the file, and the demonstrated consequence is termination of that UPX process rather than host-wide service loss.

The record

CVE
CVE-2021-46179
Published
Aug 22, 2023
Updated
Oct 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-617, T1204.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 22, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
6.5UbuntuCVSS:3.1/AV:N/AC:L/PR:N/UI:R/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-617Reachable Assertion
T1204.002User Execution: Malicious File

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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