CVE-2021-35516Network attack vector

Service crash via unchecked 7Z entry allocation

Published Jul 13, 2021 · Updated Aug 4, 2024

Uncontrolled memory allocation in Apache Commons Compress 1.6 through 1.20 allows attackers to crash Java services via crafted 7Z archives. SevenZFile.readFilesInfo eagerly allocates entry metadata from archive-controlled counts before enforcing sanity checks or configured memory limits. Exploitation requires an application to parse the supplied archive with the sevenz package; heap exhaustion interrupts that application's service.

CVSS severity7.5
High
EPSS probability12.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled memory allocation in Apache Commons Compress 1.6 through 1.20 allows attackers to crash Java services via crafted 7Z archives. SevenZFile.readFilesInfo eagerly allocates entry metadata from archive-controlled counts before enforcing sanity checks or configured memory limits. Exploitation requires an application to parse the supplied archive with the sevenz package; heap exhaustion interrupts that application's service.

The record

CVE
CVE-2021-35516
Published
Jul 13, 2021
Updated
Aug 4, 2024
Vendor
The Apache Software Foundation
Product
Apache Commons Compress
Classifications
CWE-770, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 13, 2021CVE 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=1.6 <Apache Commons Compress*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Commons Compressversion=1.6 <Apache Commons Compress*

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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