CVE-2020-27787Public exploit

Process crash via missing DT_SYMTAB validation

Published Aug 18, 2022 · Updated Aug 4, 2024

Out-of-bounds memory access in UPX before 3.96 allows local users to crash the process by decompressing a crafted ELF file. PackLinuxElf64::invert_pt_dynamic treats a missing DT_SYMTAB entry as an array index and dereferences dynp0[-1], producing an invalid read. Triggering the crash requires a local user to make UPX decompress the crafted file; the demonstrated consequence is process termination only.

CVSS severity5.5
Medium
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds memory access in UPX before 3.96 allows local users to crash the process by decompressing a crafted ELF file. PackLinuxElf64::invert_pt_dynamic treats a missing DT_SYMTAB entry as an array index and dereferences dynp0[-1], producing an invalid read. Triggering the crash requires a local user to make UPX decompress the crafted file; the demonstrated consequence is process termination only.

The record

CVE
CVE-2020-27787
Published
Aug 18, 2022
Updated
Aug 4, 2024
Vendor
The UPX Team
Product
UPX
Classifications
CWE-119, T1204.002
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

5.5NVDCVSS: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-119Improper Restriction of Operations within the Bounds of a Memory Buffer
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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