CVE-2021-45444: In zsh before 5.8.1, an attacker can achieve code execution if they control a command output inside the prompt

Q: How do I fix CVE-2021-45444?

zsh: upgrade to 5.8.1; fedora: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-45444 being exploited?

CVE-2021-45444 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-45444 affect?

CVE-2021-45444 affects zsh, fedora, debian linux. Severity is high (CVSS 7.8). 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.

Q: How urgent is CVE-2021-45444?

Priority 52/100. High severity; On your watchlist

This month

HIGH 7.8WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2021-45444 is a high-severity flaw (CVSS 7.8) affecting zsh, fedora, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	2.0% (top 19%)
CISA exploited list	No
Published	2022-02-14
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: apple · debian · fedoraproject · zsh

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-02-14 12:15 UTCPublished CVE record published
2026-06-17 04:13 UTCUpdated Record last modified

zsh zsh UPGRADE

Affected: < 5.8.1

Fixed in: 5.8.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy zsh || rpm -q zsh || zsh --version

2. UPGRADE to 5.8.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade zsh

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade zsh

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

fedoraproject fedora MITIGATE

Affected: 34 · 35

Fixed in: no fixed release known

Safe to downgrade to: a release before 34

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

debian debian linux MITIGATE

Affected: 9.0 · 10.0 · 11.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

apple mac os x UPGRADE

Affected: >= 10.15 and < 10.15.7 · 10.15.7 security_update_2020 · 10.15.7 security_update_2020-001 · 10.15.7 security_update_2020-005 · 10.15.7 security_update_2020-007 · 10.15.7 security_update_2021-001 · 10.15.7 security_update_2021-002 · 10.15.7 security_update_2021-003

Fixed in: 10.15.7

Safe to downgrade to: a release before 10.15

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

apple macos UPGRADE

Affected: >= 11.0 and < 11.6.6 · >= 12.0.0 and < 12.4

Fixed in: 11.6.6, 12.4

Safe to downgrade to: a release before 11.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-45444?

zsh: upgrade to 5.8.1; fedora: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-45444 being exploited?

CVE-2021-45444 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-45444 affect?

CVE-2021-45444 affects zsh, fedora, debian linux. Severity is high (CVSS 7.8). 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.

How urgent is CVE-2021-45444?

Priority 52/100. High severity; On your watchlist

Software pages

Debian vulnerabilities · macOS vulnerabilities

References

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