What is CVE-2018-1100?

CVE-2018-1100 is a high-severity vulnerability in Zsh, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 7.8/10. Published 2018-04-11.

How severe is CVE-2018-1100?

High severity. CVSS v3 base score is 7.8 out of 10.

Is CVE-2018-1100 known to be exploited?

3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Buffer overflow in Zsh

CVE-2018-1100

zsh through version 5.4.2 is vulnerable to a stack-based buffer overflow in the utils.c:checkmailpath function. A local attacker could exploit this to execute arbitrary code in the context of another user.

Vulnerability class: Buffer Overflow

Published 2018-04-11 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.005 (42.8th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 42.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: -0.000

Affected products

Zsh — versions through 5.4.2
Canonical Ubuntu Linux — versions 14.04, 16.04, 18.04
Red Hat Enterprise Linux Desktop — versions 6.0, 7.0
Red Hat Enterprise Linux Server — versions 6.0, 7.0
Red Hat Enterprise Linux Workstation — versions 6.0, 7.0

Weakness classification (CWE)

Public proof-of-concept exploits

References

sourceforge.net/p/zsh/code/ci/31f72205630687c1cef89347863aab355296a27f/ (Patch)
usn.ubuntu.com/3764-1/ (vendor-advisory, Third Party Advisory)
security.gentoo.org/glsa/201805-10 (vendor-advisory, Third Party Advisory)
access.redhat.com/errata/RHSA-2018:1932 (vendor-advisory, Third Party Advisory)
bugzilla.redhat.com/show_bug.cgi (Third Party Advisory, Issue Tracking)
access.redhat.com/errata/RHSA-2018:3073 (vendor-advisory, Third Party Advisory)
lists.debian.org/debian-lts-announce/2020/12/msg00000.html (mailing-list)

Frequently asked questions

What is CVE-2018-1100?: CVE-2018-1100 is a high-severity vulnerability in Zsh, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 7.8/10. Published 2018-04-11.
How severe is CVE-2018-1100?: High severity. CVSS v3 base score is 7.8 out of 10.
Is CVE-2018-1100 known to be exploited?: 3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.