CVE-2021-45444

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.

Published: 2022-02-14 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-45444 is rated Moderate Risk (60.3/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.98%). EPSS rose +1.87% over the last day, indicating growing attacker interest. 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-2021-45444

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 2026-06-15 0.11% 1.98% +1.87%
2 2025-11-21 1.26% 0.11% -1.14%
3 2025-11-18 — 1.26% —

Full EPSS history (17 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-45444

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.8 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
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:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.9 [email protected]
5.1 2.0 MEDIUM
AV:N/AC:H/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:H)
Exploitation requires uncommon or highly specific conditions.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 4.9 6.4 [email protected]

Weakness enumeration for CVE-2021-45444

OS Trackers for CVE-2021-45444

vendor priority summary link
alpine high CVE-2021-45444: 1 source package rows (zsh); 18 state rows across 8 repos (3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 8, open 10. https://security.alpinelinux.org/vuln/CVE-2021-45444
debian not yet assigned CVE-2021-45444 not yet assigned priority: Debian including 1 source packages (zsh), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-45444
gentoo normal CVE-2021-45444: 1 GLSA(s) (202407-01), 1 atom(s) (app-shells/zsh); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-45444
redhat medium — https://access.redhat.com/security/cve/CVE-2021-45444
suse high CVE-2021-45444 severity important: SUSE including 243 source package names (amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, amazon/suse-sles-15-sp1-chost-byos-v20220127-hvm-ssd-x86_64, …), 427 product×package rows across 192 product lines (HPE Helion OpenStack 8, Image SLES12-SP5-Azure-BYOS, … (192 product lines)): Known Affected 231, Fixed 193, Known Not Affected 3. https://www.suse.com/security/cve/CVE-2021-45444/
ubuntu low CVE-2021-45444 low priority: Ubuntu including 1 source packages (zsh), 14 status rows across 14 suites (bionic, focal, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 7, released 5, ignored 1, needs-triage 1. https://ubuntu.com/security/CVE-2021-45444

Affected software / configurations for CVE-2021-45444

Vendor Product Version Raw CPE
zsh zsh < 5.8.1 cpe:2.3:a:zsh:zsh:*:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
fedoraproject fedora 35 cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
debian debian_linux 11.0 cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
apple mac_os_x >= 10.15, < 10.15.7 cpe:2.3:o:apple:mac_os_x:*:*:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2020:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2020-001:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2020-005:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2020-007:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-001:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-002:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-003:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-006:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-007:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-008:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2022-001:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2022-002:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2022-003:*:*:*:*:*:*
apple macos >= 11.0, < 11.6.6 cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*
apple macos >= 12.0.0, < 12.4 cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*

References for CVE-2021-45444

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