CVE-2020-21047

Application crash via unchecked i386 disassembly bounds

Published Aug 22, 2023 · Updated Oct 7, 2024

Out-of-bounds write in elfutils 0.177 libcpu allows context-dependent attackers to crash applications via a crafted ELF file. The i386 disassembler reads a SIB byte without first confirming its parameter cursor remains before the input end, while FCT_sel accepts a two-byte operand ending at the boundary. The file must reach libasm's i386 disassembly path and be opened by a user; successful exploitation terminates the consuming process without reported confidentiality or integrity impact.

CVSS severity5.5
Medium
EPSS probability0.24%
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 write in elfutils 0.177 libcpu allows context-dependent attackers to crash applications via a crafted ELF file. The i386 disassembler reads a SIB byte without first confirming its parameter cursor remains before the input end, while FCT_sel accepts a two-byte operand ending at the boundary. The file must reach libasm's i386 disassembly path and be opened by a user; successful exploitation terminates the consuming process without reported confidentiality or integrity impact.

The record

CVE
CVE-2020-21047
Published
Aug 22, 2023
Updated
Oct 7, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 22, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 7, 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 vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
5.5IBMCVSS:3.0/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1204.002User Execution: Malicious File

Public exploit references

No public exploit references are available in this record.

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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