What is CVE-2018-0502?

CVE-2018-0502 is a critical-severity vulnerability in Zsh, classified under Improper Input Validation. CVSS score: 9.8/10. Published 2018-09-05.

How severe is CVE-2018-0502?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Improper input validation in Zsh

CVE-2018-0502

An issue was discovered in zsh before 5.6. The beginning of a #! script file was mishandled, potentially leading to an execve call to a program named on the second line.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2018-09-05 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.025 (84.1th percentile), scored 2026-10-03.

Low probability of exploitation in the next 30 days, but still tracked. 84th percentile — 84.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.025 · newest: 0.025 · change: 0.000

Affected products

Zsh
Canonical Ubuntu Linux — versions 14.04, 16.04, 18.04
Zsh Before 5.6 — versions zsh before 5.6

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

bugs.debian.org/908000 (Patch, Mailing List, Third Party Advisory)
sourceforge.net/p/zsh/code/ci/1c4c7b6a4d17294df028322b70c53803a402233d (Patch, Third Party Advisory)
www.zsh.org/mla/zsh-announce/136 (Mailing List, Vendor Advisory)
usn.ubuntu.com/3764-1/ (vendor-advisory, Third Party Advisory)
security.gentoo.org/glsa/201903-02 (vendor-advisory, Third Party Advisory)
lists.debian.org/debian-lts-announce/2020/12/msg00000.html (mailing-list)

Frequently asked questions

What is CVE-2018-0502?: CVE-2018-0502 is a critical-severity vulnerability in Zsh, classified under Improper Input Validation. CVSS score: 9.8/10. Published 2018-09-05.
How severe is CVE-2018-0502?: Critical severity. CVSS v3 base score is 9.8 out of 10.