CVE-2017-18206 [Critical] | Memory Corruption in Zsh

CVE-2017-18206 is rated Moderate Risk (60/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 0.40%). Review affected assets and schedule remediation.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-01-27	0.51%	0.40%	-0.12%
2	2025-11-30	1.07%	0.51%	-0.55%
3	2025-10-26	—	1.07%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-01-27

0.51%

0.40%

-0.12%

2025-11-30

1.07%

0.51%

-0.55%

2025-10-26

—

1.07%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
9.8	3.0	CRITICAL	`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. 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:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. 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.	3.9	5.9	[email protected]
7.5	2.0	HIGH	`AV:N/AC:L/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:L) Exploitation conditions are straightforward and predictable. 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.	10.0	6.4	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

9.8

3.0

CRITICAL

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
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.

3.9

5.9

[email protected]

7.5

2.0

HIGH

AV:N/AC:L/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:L): Exploitation conditions are straightforward and predictable.
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.

10.0

6.4

[email protected]

OS Trackers for CVE-2017-18206

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2017-18206 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-2017-18206
`gentoo`	normal	CVE-2017-18206: 1 GLSA(s) (201805-10), 1 atom(s) (app-shells/zsh); latest impact normal.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2017-18206
`redhat`	low	—	https://access.redhat.com/security/cve/CVE-2017-18206
`suse`	medium	CVE-2017-18206 severity moderate: SUSE including 5 source package names (zsh, zsh-4.3.6-67.9.8.1, zsh-5.0.2-31.el7, zsh-5.0.5-6.7.2, zsh-html-5.0.2-31.el7), 47 product×package rows across 46 product lines (Image SLES12-SP5-Azure-BYOS, Image SLES12-SP5-Azure-Basic-On-Demand, … (46 product lines)): Fixed 28, Known Not Affected 18, Will Not Fix 1.	https://www.suse.com/security/cve/CVE-2017-18206/
`ubuntu`	medium	CVE-2017-18206 medium priority: Ubuntu including 1 source packages (zsh), 4 status rows across 4 suites (artful, trusty, upstream, xenial): released 2, DNE 1, needs-triage 1.	https://ubuntu.com/security/CVE-2017-18206

Affected software / configurations for CVE-2017-18206

Vendor	Product	Version	Raw CPE
zsh	zsh	< 5.4	cpe:2.3:a:zsh:zsh::::::::
canonical	ubuntu_linux	14.04	cpe:2.3:o:canonical:ubuntu_linux:14.04::::lts:::
canonical	ubuntu_linux	16.04	cpe:2.3:o:canonical:ubuntu_linux:16.04::::lts:::
canonical	ubuntu_linux	17.10	cpe:2.3:o:canonical:ubuntu_linux:17.10:::::::*

References for CVE-2017-18206

URL	Tags
https://access.redhat.com/errata/RHSA-2018:1932	Third Party Advisory
https://access.redhat.com/errata/RHSA-2018:3073	Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/12/msg00000.html
https://security.gentoo.org/glsa/201805-10	Third Party Advisory
https://sourceforge.net/p/zsh/code/ci/c7a9cf465dd620ef48d586026944d9bd7a0d5d6d	Patch Third Party Advisory
https://usn.ubuntu.com/3593-1/	Third Party Advisory

URL

CVE-2017-18206

Exploit prediction scoring system (EPSS) score for CVE-2017-18206

Common vulnerability scoring system (CVSS) metrics for CVE-2017-18206

Weakness enumeration for CVE-2017-18206

OS Trackers for CVE-2017-18206

Affected software / configurations for CVE-2017-18206

References for CVE-2017-18206