CVE-2020-27790Public exploit

Process crash via unchecked ELF symbol size

Published Aug 18, 2022 · Updated Aug 4, 2024

Divide by zero in PackLinuxElf64::invert_pt_dynamic in UPX before 3.96 allows context-dependent attackers to crash UPX with a crafted ELF file. The function trusts the ELF DT_SYMENT entry as a symbol size and divides the distance between DT_STRTAB and DT_SYMTAB by that unvalidated value. A user must process the crafted file with UPX; a zero or undersized DT_SYMENT value raises SIGFPE and terminates that UPX process.

CVSS severity5.5
Medium
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Divide by zero in PackLinuxElf64::invert_pt_dynamic in UPX before 3.96 allows context-dependent attackers to crash UPX with a crafted ELF file. The function trusts the ELF DT_SYMENT entry as a symbol size and divides the distance between DT_STRTAB and DT_SYMTAB by that unvalidated value. A user must process the crafted file with UPX; a zero or undersized DT_SYMENT value raises SIGFPE and terminates that UPX process.

The record

CVE
CVE-2020-27790
Published
Aug 18, 2022
Updated
Aug 4, 2024
Vendor
The UPX Team
Product
UPX
Classifications
CWE-369, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 18, 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=Fixed in v3.96.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The UPX Team · UPXversion=Fixed in v3.96.

Published CVSS scores

5.5UbuntuCVSS:3.1/AV:L/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-369Divide By Zero
T1499.004Application or System Exploitation

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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