CVE-2021-33645Network attack vector

Service interruption via unreleased GNU long-link buffers

Published Aug 9, 2022 · Updated Nov 3, 2025

Memory leak in th_read() in Feep libtar before 1.2.21 allows remote attackers to exhaust memory through crafted tar archives. th_read() allocates gnu_longlink storage for GNU long-link headers, but tar_close() fails to release that buffer when closing the TAR handle. Exploitation requires an application to accept attacker-supplied archives and repeatedly open and close handles, causing memory exhaustion and service interruption.

CVSS severity7.5
High
EPSS probability1.79%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory leak in th_read() in Feep libtar before 1.2.21 allows remote attackers to exhaust memory through crafted tar archives. th_read() allocates gnu_longlink storage for GNU long-link headers, but tar_close() fails to release that buffer when closing the TAR handle. Exploitation requires an application to accept attacker-supplied archives and repeatedly open and close handles, causing memory exhaustion and service interruption.

The record

CVE
CVE-2021-33645
Published
Aug 9, 2022
Updated
Nov 3, 2025
Vendor
Feep
Product
libtar
Classifications
CWE-401, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 9, 2022CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record 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=<1.2.21

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Feep · libtarversion=<1.2.21

Published CVSS scores

7.5UbuntuCVSS: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

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-401Missing Release of Memory after Effective Lifetime
T1499.004Application or System Exploitation

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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