CVE-2021-33644

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_longname, causing an out-of-bounds read.

Published: 2022-08-10 Last update: 2025-11-03 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-33644 is rated Moderate Risk (49.1/100): CVSS High severity, with low exploitation likelihood (EPSS 0.24%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-33644

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-25 0.27% 0.24% -0.03%
2 2026-05-10 0.19% 0.27% +0.08%
3 2025-11-21 — 0.19% —

Full EPSS history (16 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-33644

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.1 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.2 [email protected]

Weakness enumeration for CVE-2021-33644

OS Trackers for CVE-2021-33644

vendor priority summary link
alpine — CVE-2021-33644: 1 source package rows (libtar); 2 state rows across 2 repos (3.17-community, 3.18-community); fixed 0, open 2. https://security.alpinelinux.org/vuln/CVE-2021-33644
debian not yet assigned CVE-2021-33644 not yet assigned priority: Debian including 1 source packages (libtar), 2 status rows across 2 suites (bookworm, bullseye): resolved 2. https://security-tracker.debian.org/tracker/CVE-2021-33644
redhat medium — https://access.redhat.com/security/cve/CVE-2021-33644
ubuntu medium CVE-2021-33644 medium priority: Ubuntu including 1 source packages (libtar), 12 status rows across 12 suites (bionic, focal, jammy, kinetic, lunar, mantic, noble, oracular, plucky, trusty, upstream, xenial): released 6, ignored 4, DNE 2. https://ubuntu.com/security/CVE-2021-33644

Affected software / configurations for CVE-2021-33644

Vendor Product Version Raw CPE
feep libtar < 1.2.21 cpe:2.3:a:feep:libtar:*:*:*:*:*:*:*:*
openatom openeuler 20.03 cpe:2.3:o:openatom:openeuler:20.03:sp1:*:*:lts:*:*:*
openatom openeuler 20.03 cpe:2.3:o:openatom:openeuler:20.03:sp3:*:*:lts:*:*:*
openatom openeuler 22.03 cpe:2.3:o:openatom:openeuler:22.03:*:*:*:lts:*:*:*
fedoraproject fedora 35 cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
fedoraproject fedora 36 cpe:2.3:o:fedoraproject:fedora:36:*:*:*:*:*:*:*
fedoraproject fedora 37 cpe:2.3:o:fedoraproject:fedora:37:*:*:*:*:*:*:*

References for CVE-2021-33644

URL Tags
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4S4PJRCJLEAWN2EKXGLSOBTL7O57V7NC/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5YSHZY753R7XW6CIKJVAWI373WW3YRRJ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/7Q26QDNOJDOFYWMJWEIK5XR62M2FF6IJ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/7WX5YE66CT7Y5C2HTHXSFDKQWYWYWJ2T/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OD4HEBSTI22FNYKOKK7W3X6ZQE6FV3XC/
https://www.openeuler.org/en/security/safety-bulletin/detail.html?id=openEuler-SA-2022-1807 Third Party Advisory
https://lists.debian.org/debian-lts-announce/2025/01/msg00026.html
cvelogic Threat Intelligence