CVE-2018-13259 [Critical] | Input Validation Bypass in Ubuntu Linux

CVE-2018-13259 is rated Moderate Risk (63.5/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 0.65%). Review affected assets and schedule remediation.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-04-13	1.12%	0.65%	-0.47%
2	2026-03-22	1.22%	1.12%	-0.10%
3	2025-05-17	—	1.22%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-04-13

1.12%

0.65%

-0.47%

2026-03-22

1.22%

1.12%

-0.10%

2025-05-17

—

1.22%

—

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-2018-13259

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2018-13259 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-2018-13259
`gentoo`	normal	CVE-2018-13259: 1 GLSA(s) (201903-02), 1 atom(s) (app-shells/zsh); latest impact normal.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2018-13259
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2018-13259
`suse`	high	CVE-2018-13259 severity important: SUSE including 246 source package names (amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, amazon/suse-sles-15-sp1-chost-byos-v20220127-hvm-ssd-x86_64, …), 310 product×package rows across 71 product lines (HPE Helion OpenStack 8, Image SLES12-SP5-Azure-BYOS, … (71 product lines)): Known Affected 231, Fixed 54, Known Not Affected 25.	https://www.suse.com/security/cve/CVE-2018-13259/
`ubuntu`	medium	CVE-2018-13259 medium priority: Ubuntu including 1 source packages (zsh), 4 status rows across 4 suites (bionic, trusty, upstream, xenial): released 4.	https://ubuntu.com/security/CVE-2018-13259

Affected software / configurations for CVE-2018-13259

Vendor	Product	Version	Raw CPE
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	18.04	cpe:2.3:o:canonical:ubuntu_linux:18.04::::lts:::
zsh	zsh	< 5.6	cpe:2.3:a:zsh:zsh::::::::

References for CVE-2018-13259

URL	Tags
https://access.redhat.com/errata/RHSA-2019:2017
https://bugs.debian.org/908000	Mailing List Patch Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/12/msg00000.html
https://security.gentoo.org/glsa/201903-02	Third Party Advisory
https://sourceforge.net/p/zsh/code/ci/1c4c7b6a4d17294df028322b70c53803a402233d	Patch Third Party Advisory
https://usn.ubuntu.com/3764-1/	Third Party Advisory
https://www.zsh.org/mla/zsh-announce/136	Mailing List Release Notes Vendor Advisory

URL

CVE-2018-13259

Exploit prediction scoring system (EPSS) score for CVE-2018-13259

Common vulnerability scoring system (CVSS) metrics for CVE-2018-13259

Weakness enumeration for CVE-2018-13259

OS Trackers for CVE-2018-13259

Affected software / configurations for CVE-2018-13259

References for CVE-2018-13259