CVE-2020-9391Public exploit

Local heap corruption via tagged brk address

Published Feb 25, 2020 · Updated Aug 4, 2024

Memory corruption in the AArch64 Linux kernel 5.4 and 5.5 through 5.5.6 allows local users to corrupt a glibc heap via brk. The arm64 brk path strips the top address byte instead of rejecting an address beyond the 56-bit limit, allowing the program break to move downward when malloc expects an upward move. Reachability requires an AArch64 system and a local process using glibc malloc; the demonstrated consequence is process heap corruption and a crash.

CVSS severity5.5
Medium
EPSS probability0.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in the AArch64 Linux kernel 5.4 and 5.5 through 5.5.6 allows local users to corrupt a glibc heap via brk. The arm64 brk path strips the top address byte instead of rejecting an address beyond the 56-bit limit, allowing the program break to move downward when malloc expects an upward move. Reachability requires an AArch64 system and a local process using glibc malloc; the demonstrated consequence is process heap corruption and a crash.

The record

CVE
CVE-2020-9391
Published
Feb 25, 2020
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 25, 2020CVE 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

2.1NIST NVDAV:L/AC:L/Au:N/C:N/I:N/A:P
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
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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