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Fencer Intel
critical 9.8

CVE-2017-18206 json

In utils.c in zsh before 5.4, symlink expansion had a buffer overflow.

published 2018-02-27 8 y ago modified 2026-06-17 4 mo ago also EUVD-2017-9339

cvss
9.8
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.1%
EPSS 3.1% chance of exploitation in 30 days, percentile 87%
public exploits
0
none known

Summary

In utils.c in zsh before 5.4, symlink expansion had a buffer overflow.

Patch / fix

  • zsh zsh 5.4
  • zsh Debian 14, Debian 13, Debian 12 5.4.1-1

debian advisories DEBIAN-CVE-2017-18206

  • zsh Ubuntu 16.04 LTS 5.1.1-1ubuntu2.1

ubuntu advisories UBUNTU-CVE-2017-18206

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • zsh RHEL 6 4.3.11-8.el6
  • zsh-html RHEL 6 4.3.11-8.el6
  • zsh RHEL 7 5.0.2-31.el7
  • zsh-html RHEL 7 5.0.2-31.el7

red hat advisories RHSA-2018:1932RHSA-2018:3073

  • zsh SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 4.3.6-67.9.8.1
  • zsh SLES for SAP 12 SP3, SLES 12 SP3, SLED 12 SP3 5.0.5-6.7.2

suse advisories SUSE-SU-2022:14910-1SUSE-SU-2018:1072-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2017-18206 updated cvss 7.5

zsh: buffer overrun in symlinks

  • Red Hat Enterprise Linux 5 zsh
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux Client (v. 7) zsh 5.0.2-31.el7 Red Hat Enterprise Linux Client Optional (v. 7) zsh-html 5.0.2-31.el7 Red Hat Enterprise Linux ComputeNode (v. 7) zsh 5.0.2-31.el7 Red Hat Enterprise Linux ComputeNode Optional (v. 7) zsh-html 5.0.2-31.el7
    fixed: vendor fix RHSA-2018:3073
  • Red Hat Enterprise Linux Desktop (v. 6) zsh 4.3.11-8.el6 Red Hat Enterprise Linux Desktop Optional (v. 6) zsh-html 4.3.11-8.el6
    fixed: vendor fix RHSA-2018:1932
  • Red Hat Enterprise Linux for ARM and IBM Power LE (POWER9) Server (v. 7) zsh 5.0.2-31.el7 Red Hat Enterprise Linux for ARM and IBM Power LE (POWER9) Server Optional (v. 7) zsh-html 5.0.2-31.el7
    fixed: vendor fix RHSA-2018:3073
  • Red Hat Enterprise Linux HPC Node (v. 6) zsh 4.3.11-8.el6 Red Hat Enterprise Linux HPC Node Optional (v. 6) zsh-html 4.3.11-8.el6 Red Hat Enterprise Linux Server (v. 6) zsh 4.3.11-8.el6
    fixed: vendor fix RHSA-2018:1932
  • Red Hat Enterprise Linux Server (v. 7) zsh 5.0.2-31.el7
    fixed: vendor fix RHSA-2018:3073
  • Red Hat Enterprise Linux Server Optional (v. 6) zsh-html 4.3.11-8.el6
    fixed: vendor fix RHSA-2018:1932
  • Red Hat Enterprise Linux Server Optional (v. 7) zsh-html 5.0.2-31.el7
    fixed: vendor fix RHSA-2018:3073
show 5 more
  • Red Hat Enterprise Linux Workstation (v. 6) zsh 4.3.11-8.el6
    fixed: vendor fix RHSA-2018:1932
  • Red Hat Enterprise Linux Workstation (v. 7) zsh 5.0.2-31.el7
    fixed: vendor fix RHSA-2018:3073
  • Red Hat Enterprise Linux Workstation Optional (v. 6) zsh-html 4.3.11-8.el6
    fixed: vendor fix RHSA-2018:1932
  • Red Hat Enterprise Linux Workstation Optional (v. 7) zsh-html 5.0.2-31.el7
    fixed: vendor fix RHSA-2018:3073
  • Red Hat Enterprise Linux 8 zsh, zsh-html
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

3.11% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.0 9.8 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Classification

Weakness
  • CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.