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CVE-2026-55999

36
FAUCET Score

Local attackers with a X connection able to provide PCX fonts to the X server xorg-server before 21.2.24 and xwayland before 24.1.13 could cause a heap buffer overflow via SetFont due to missing glyph boundary checks.

First published: Jul 8, 2026Last modified: Jul 8, 2026

Impacted Technologies

VendorProductVersion(s)CPE
< 21.2.24CPE matchmatch criteria
cpe:2.3:a:x.org:x_server:*:*:*:*:*:*:*:*
< 24.1.13CPE matchmatch criteria
cpe:2.3:a:x.org:xwayland:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.5HIGH

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
1.8
Impact Score
6.0
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.27%
Probability of exploitation in next 30 days
EPSS Percentile
18.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0027 is in the 54th percentile among its peer group of 17,070 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.2 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Advisories (1)

microsoft2026-Jul/CVE-2026-55999Important

xorg-server / xwayland glamor font atlas Heap Buffer Overflow

Jul 2, 2026

References

gitlab.freedesktop.org / xorg/xserver/-/commit/fbf7bac22e2c6bd627fb042742a23318263edae1
Patch
openwall.com / lists/oss-security/2026/07/08/2
Mailing ListPatchThird Party Advisory