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CVE-2021-45444

27
FAUCET Score

CVE-2021-45444 describes a critical code execution vulnerability in zsh versions prior to 5.8.1, impacting products like Apple, Debian, and Fedora. An attacker can exploit this by controlling command output within the prompt, leveraging recursive PROMPT_SUBST expansion. With a CVSS score of 7.8 (High), this vulnerability allows for high impact to confidentiality, integrity, and availability with low attack complexity, requiring user interaction. While no public exploits (Metasploit, Nuclei, ExploitDB) or active exploitation (KEV) have been identified, and community discussion is minimal, the potential for severe consequences warrants attention.

Impacted Technologies

VendorProductVersion(s)CPE
< 5.8.1CPE matchmatch criteria
cpe:2.3:a:zsh:zsh:*:*:*:*:*:*:*:*
34CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
35CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.8HIGH

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

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
1.8
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.98%
Probability of exploitation in next 30 days
EPSS Percentile
78.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0198 is in the 77th percentile among its peer group of 11,621 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.2 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 (5)

microsoftpatch availablevia msrc
Product: 18899-16820Fixed in: 5.8.1-1
microsoftpatch availablevia msrc
Product: 18900-16823Fixed in: 5.9-1
microsoftpatch availablevia msrc
Product: cm1 zsh 5.8.1-1 on CBL Mariner 1.0Fixed in: 5.8.1-1
microsoftpatch availablevia msrc
Product: cbl2 zsh 5.9-1 on CBL Mariner 2.0Fixed in: 5.9-1
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: zsh-0:5.5.1-9.el8
View patch

Vendor Advisories (2)

redhatCVE-2021-45444Moderate

zsh: Prompt expansion vulnerability

Feb 12, 2022
microsoft2022-Feb/CVE-2021-45444Important

In zsh before 5.8.1 an attacker can achieve code execution if they control a command output inside the prompt as demonstrated by a %F argument. This occurs because of recursive PROMPT_SUBST expansion.

Feb 8, 2022

References

seclists.org / fulldisclosure/2022/May/33
Mailing ListThird Party Advisory
seclists.org / fulldisclosure/2022/May/35
Mailing ListThird Party Advisory
seclists.org / fulldisclosure/2022/May/38
Mailing ListThird Party Advisory
lists.debian.org / debian-lts-announce/2022/02/msg00020.html
Mailing ListThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/2P3LPMGENEHKDWFO4MWMZSZL6G7Y4CV7
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/BWF3EXNBX5SVFDBL4ZFOD4GJBWFUKWN4
support.apple.com / kb/HT213255
Third Party Advisory
support.apple.com / kb/HT213256
Third Party Advisory
support.apple.com / kb/HT213257
Third Party Advisory
vuln.ryotak.me / advisories/63
Third Party Advisory
debian.org / security/2022/dsa-5078
Third Party Advisory
zsh.sourceforge.io / releases.html
Release NotesThird Party Advisory