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CVE-2021-33643

29
FAUCET Score

CVE-2021-33643 is a critical vulnerability affecting libtar and related Fedora/OpenEuler products, allowing an unauthenticated attacker to trigger an out-of-bounds read. By submitting a specially crafted tar file with a zero-sized header, an attacker can cause a malloc(0) call, leading to a denial of service or potentially information disclosure. With a CVSS score of 9.1 (CRITICAL), this vulnerability poses a significant risk due to its network-based attack vector and low attack complexity. Currently, there is no public exploit code available, and it is not known to be actively exploited, with minimal community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.2.21CPE matchmatch criteria
cpe:2.3:a:feep:libtar:*:*:*:*:*:*:*:*
20.03CPE matchmatch criteria
cpe:2.3:o:openatom:openeuler:20.03:sp1:*:*:lts:*:*:*
20.03CPE matchmatch criteria
cpe:2.3:o:openatom:openeuler:20.03:sp3:*:*:lts:*:*:*
22.03CPE matchmatch criteria
cpe:2.3:o:openatom:openeuler:22.03:*:*:*:lts:*:*:*
35CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.1CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.2
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.34%
Probability of exploitation in next 30 days
EPSS Percentile
68.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
This CVE's current EPSS score of 0.0134 is in the 55th percentile among its peer group of 36,833 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (13)

microsoftpatch availablevia msrc
Product: Azure Linux 3.0 ARMFixed in: 1.2.20-11
microsoftpatch availablevia msrc
Product: 18871-16823Fixed in: 1.2.20-10
microsoftpatch availablevia msrc
Product: 18850-17084Fixed in: 1.2.20-11
microsoftpatch availablevia msrc
Product: 18870-16820Fixed in: 1.2.20-10
microsoftpatch availablevia msrc
Product: cm1 libtar 1.2.20-10 on CBL Mariner 1.0Fixed in: 1.2.20-10
microsoftpatch availablevia msrc
Product: cbl2 libtar 1.2.20-10 on CBL Mariner 2.0Fixed in: 1.2.20-10
microsoftpatch availablevia msrc
Product: azl3 libtar 1.2.20-11 on Azure Linux 3.0Fixed in: 1.2.20-11
microsoftpatch availablevia msrc
Product: CBL Mariner 1.0 x64Fixed in: 1.2.20-10
microsoftpatch availablevia msrc
Product: CBL Mariner 1.0 ARMFixed in: 1.2.20-10
microsoftpatch availablevia msrc
Product: CBL Mariner 2.0 x64Fixed in: 1.2.20-10
microsoftpatch availablevia msrc
Product: CBL Mariner 2.0 ARMFixed in: 1.2.20-10
microsoftpatch availablevia msrc
Product: Azure Linux 3.0 x64Fixed in: 1.2.20-11
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: libtar-0:1.2.20-17.el8
View patch

Vendor Advisories (3)

microsoft2024-Jun/CVE-2021-33643

CVE-2021-33643

Jun 11, 2024
redhatCVE-2021-33643Moderate

libtar: out-of-bounds read in gnu_longlink

Aug 10, 2022
microsoft2022-Aug/CVE-2021-33643Critical

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.

Aug 9, 2022

References

lists.debian.org / debian-lts-announce/2025/01/msg00026.html
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/4S4PJRCJLEAWN2EKXGLSOBTL7O57V7NC
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/5YSHZY753R7XW6CIKJVAWI373WW3YRRJ
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/7Q26QDNOJDOFYWMJWEIK5XR62M2FF6IJ
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/7WX5YE66CT7Y5C2HTHXSFDKQWYWYWJ2T
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/OD4HEBSTI22FNYKOKK7W3X6ZQE6FV3XC
openeuler.org / en/security/safety-bulletin/detail.html
Broken LinkThird Party Advisory