CVE-2020-27796Public exploit

Process abort via dynamic-segment heap over-read

Published Aug 25, 2022 · Updated Aug 4, 2024

Heap-based buffer over-read in UPX 4.0.0 allows context-dependent attackers to abort the process through a crafted Mach-O file. PackLinuxElf32::invert_pt_dynamic reads four bytes beyond the heap allocation while parsing dynamic-segment data during decompression. Exploitation requires a user to run upx -d on the crafted file; the demonstrated consequence is an AddressSanitizer-detected abort.

CVSS severity7.8
High
EPSS probability0.34%
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 over-read in UPX 4.0.0 allows context-dependent attackers to abort the process through a crafted Mach-O file. PackLinuxElf32::invert_pt_dynamic reads four bytes beyond the heap allocation while parsing dynamic-segment data during decompression. Exploitation requires a user to run upx -d on the crafted file; the demonstrated consequence is an AddressSanitizer-detected abort.

The record

CVE
CVE-2020-27796
Published
Aug 25, 2022
Updated
Aug 4, 2024
Vendor
The UPX Team
Product
UPX
Classifications
CWE-119, CWE-125, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 25, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

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

  1. Affected versionversion=upx 4.0.0-git-87b73e5cfdc1+

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The UPX Team · UPXversion=upx 4.0.0-git-87b73e5cfdc1+

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-125Out-of-bounds Read
T1204.002Malicious 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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