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CVE-2021-33640

31
FAUCET Score

CVE-2021-33640 is a critical use-after-free vulnerability in libtar.c, specifically affecting Fedora and OpenEuler distributions. The flaw occurs when the tar_close() function releases memory that is subsequently accessed, leading to potential system compromise. With a CVSS score of 9.8, this vulnerability is easily exploitable over the network with no user interaction, allowing for high impact on confidentiality, integrity, and availability. While no public exploit code or active exploitation has been observed, and community discussion is minimal, the severe nature of the vulnerability warrants attention.

Impacted Technologies

VendorProductVersion(s)CPE
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:sp2:*:*:lts:*:*:*
22.03CPE matchmatch criteria
cpe:2.3:o:openatom:openeuler:22.03:*:*:*:lts:*:*:*
36CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:36:*:*:*:*:*:*:*
37CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:37:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.2MEDIUM

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

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.5
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.65%
Probability of exploitation in next 30 days
EPSS Percentile
47.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0065 is in the 28th percentile among its peer group of 36,862 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 (12)

microsoftpatch availablevia msrc
Product: 18848-16820Fixed in: 1.2.20-11
microsoftpatch availablevia msrc
Product: 18849-16823Fixed in: 1.2.20-11
microsoftpatch availablevia msrc
Product: 18850-17084Fixed in: 1.2.20-11
microsoftpatch availablevia msrc
Product: cm1 libtar 1.2.20-11 on CBL Mariner 1.0Fixed in: 1.2.20-11
microsoftpatch availablevia msrc
Product: cbl2 libtar 1.2.20-11 on CBL Mariner 2.0Fixed in: 1.2.20-11
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: 1.2.20-11
microsoftpatch availablevia msrc
Product: CBL Mariner 1.0 ARMFixed in: 1.2.20-11
microsoftpatch availablevia msrc
Product: CBL Mariner 2.0 x64Fixed in: 1.2.20-11
microsoftpatch availablevia msrc
Product: CBL Mariner 2.0 ARMFixed in: 1.2.20-11
microsoftpatch availablevia msrc
Product: Azure Linux 3.0 x64Fixed in: 1.2.20-11
microsoftpatch availablevia msrc
Product: Azure Linux 3.0 ARMFixed in: 1.2.20-11

Vendor Advisories (3)

microsoft2024-Jun/CVE-2021-33640

CVE-2021-33640

Jun 11, 2024
microsoft2022-Dec/CVE-2021-33640Critical

After tar_close() libtar.c releases the memory pointed to by pointer t. After tar_close() is called in the list() function it continues to use pointer t: free_longlink_longname(t->th_buf) . As a result the released memory is used (use-after-free).

Dec 13, 2022
redhatCVE-2021-33640Moderate

libtar: fixes for CVE-2021-33645 and CVE-2021-33646 introduced new use-after-free bugs in libtar

Dec 9, 2022

References

lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/4S4PJRCJLEAWN2EKXGLSOBTL7O57V7NC
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/7WX5YE66CT7Y5C2HTHXSFDKQWYWYWJ2T
openeuler.org / en/security/cve/detail
Vendor Advisory