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Fencer Vulns
medium 6.5

CVE-2021-33643 json

An attacker who submits a crafted tar file with size in header struct being 0 may be able to trigger an calling of malloc(0) for a variable…

published 2022-08-09 4 y ago modified 2026-06-23 4 mo ago also EUVD-2021-20320

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.9%
EPSS 1.9% chance of exploitation in 30 days, percentile 79%
public exploits
0
none known

Summary

An attacker who submits a crafted tar file with size in header struct being 0 may be able to trigger an calling of malloc(0) for a variable gnu_longlink, causing an out-of-bounds read.

Patch / fix

  • feep libtar 1.2.21
  • libtar Debian 12 1.2.20-8+deb12u1

debian advisories DEBIAN-CVE-2021-33643

  • libtar Ubuntu 20.04 LTS 1.2.20-8ubuntu0.20.04.1
  • libtar Ubuntu 22.04 LTS 1.2.20-8ubuntu0.22.04.1
  • libtar Ubuntu 24.04 LTS 1.2.20-8.1ubuntu0.24.04.1
  • libtar Ubuntu Pro 16.04 LTS 1.2.20-4ubuntu0.1~esm1
  • libtar Ubuntu Pro 18.04 LTS 1.2.20-7ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2021-33643

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libtar RHEL 8 1.2.20-17.el8

red hat advisories RHSA-2023:2898

  • libtar openSUSE Tumbleweed 1.2.20-3.1

opensuse advisories openSUSE-SU-2026:11092-1

  • libtar AlmaLinux 8 1.2.20-17.el8

almalinux advisories ALSA-2023:2898

  • libtar Rocky Linux 8 1.2.20-17.el8

rocky linux advisories RLSA-2023:2898

  • libtar CBL-Mariner 2.0 1.2.20-10
  • libtar Azure Linux 3.0 1.2.20-11

azure linux advisories AZL-10542AZL-34946

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-33643 updated cvss 7.4

libtar: out-of-bounds read in gnu_longlink

  • Red Hat Enterprise Linux 6 libtar Red Hat Enterprise Linux 7 libtar
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) libtar 1.2.20-17.el8
    fixed: vendor fix RHSA-2023:2898

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

1.88% chance of exploitation in the next 30 days, higher than 79% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
NVD 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L

Affected products

  • n/a libtar

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.