CVE-2018-15862 [Medium] | Security Vulnerability in Libxkbcommon

Unchecked NULL pointer usage in LookupModMask in xkbcomp/expr.c in xkbcommon before 0.8.2 could be used by local attackers to crash (NULL pointer dereference) the xkbcommon parser by supplying a crafted keymap file with invalid virtual modifiers.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2025-11-21	0.06%	0.04%	-0.01%
2	2025-11-18	0.04%	0.06%	+0.01%
3	2025-08-30	—	0.04%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2025-11-21

0.06%

0.04%

-0.01%

2025-11-18

0.04%

0.06%

+0.01%

2025-08-30

—

0.04%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.5	3.0	MEDIUM	`CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. 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:L) A normal user session is enough; they don’t have to be admin. 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:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.8	3.6	[email protected]
2.1	2.0	LOW	`AV:L/AC:L/Au:N/C:N/I:N/A:P` Click to expand Access vector (AV:L) Requires local access to the target system. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:N) No confidentiality impact. Integrity impact (I:N) No integrity impact. Availability impact (A:P) Partial availability impact.	3.9	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.5

3.0

MEDIUM

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

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
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:L): A normal user session is enough; they don’t have to be admin.
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:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.8

3.6

[email protected]

2.1

2.0

LOW

AV:L/AC:L/Au:N/C:N/I:N/A:P Click to expand

Access vector (AV:L): Requires local access to the target system.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:N): No confidentiality impact.
Integrity impact (I:N): No integrity impact.
Availability impact (A:P): Partial availability impact.

3.9

2.9

[email protected]

OS Trackers for CVE-2018-15862

vendor	priority	summary	link
`debian`	low	CVE-2018-15862 low priority: Debian including 1 source packages (libxkbcommon), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2018-15862
`gentoo`	normal	CVE-2018-15862: 1 GLSA(s) (201810-05), 1 atom(s) (x11-libs/libxkbcommon); latest impact normal.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2018-15862
`redhat`	low	—	https://access.redhat.com/security/cve/CVE-2018-15862
`suse`	low	CVE-2018-15862 severity low: SUSE including 327 source package names (0.38.1.5.8.45:libxkbcommon0-0.8.2-3.3.1, 0.38.1:libxkbcommon0-0.8.2-3.3.1, …), 426 product×package rows across 52 product lines (Container suse/sles/15.2/virt-handler, Container suse/sles/15.2/virt-launcher, … (52 product lines)): Known Affected 231, Fixed 170, Known Not Affected 25.	https://www.suse.com/security/cve/CVE-2018-15862/
`ubuntu`	medium	CVE-2018-15862 medium priority: Ubuntu including 1 source packages (libxkbcommon), 5 status rows across 5 suites (bionic, cosmic, trusty, upstream, xenial): released 4, not-affected 1.	https://ubuntu.com/security/CVE-2018-15862

Affected software / configurations for CVE-2018-15862

Vendor	Product	Version	Raw CPE
xkbcommon	libxkbcommon	<= 0.8.1	cpe:2.3:a:xkbcommon:libxkbcommon::::::::
xkbcommon	xkbcommon	<= 0.8.1	cpe:2.3:a:xkbcommon:xkbcommon::::::::
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:::

References for CVE-2018-15862

URL	Tags
https://access.redhat.com/errata/RHSA-2019:2079
https://github.com/xkbcommon/libxkbcommon/commit/4e2ee9c3f6050d773f8bbe05bc0edb17f1ff8371	Patch Third Party Advisory
https://lists.freedesktop.org/archives/wayland-devel/2018-August/039243.html	Mailing List Patch Third Party Advisory
https://security.gentoo.org/glsa/201810-05	Third Party Advisory
https://usn.ubuntu.com/3786-1/	Third Party Advisory
https://usn.ubuntu.com/3786-2/	Third Party Advisory

URL

CVE-2018-15862

Exploit prediction scoring system (EPSS) score for CVE-2018-15862

Common vulnerability scoring system (CVSS) metrics for CVE-2018-15862

Weakness enumeration for CVE-2018-15862

OS Trackers for CVE-2018-15862

Affected software / configurations for CVE-2018-15862

References for CVE-2018-15862