CVE
X.Org X11 Server information leak in XRes QueryClientIds
- Exploited
- No known exploitation
- Fix
- Fixed in xorg-x11-server 21.1.26 · xwayland 24.1.15
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: xorg-x11-server 21.1.26 · xwayland 24.1.15.
- Published
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 7/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
The X.Org Server and Xwayland software contain a flaw in the XRes QueryClientIds request handling, where an integer overflow causes a buffer overread. A local attacker who already has a low-privilege authenticated X client connection can use this to crash the server or leak information.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
A buffer overread caused by an integer-overflow in Proc/SProcXResQueryClientIds in X.Org xwayland before 24.1.15 and X Server before 21.1.26 could be used by attackers on authenticated X clients to crash the server or leak out information.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure?/25Unknown. No advisory context yet
- Reach?/20Unknown. No tracked technology or package matched
- Severity6.9/10CVSS 6.9
- No patch0/5No signal
What would change the score
- Would score about 62 if added to CISA KEV
- Would score about 57 if CISA's SSVC rates exploitation active
- Would score about 29 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: xorg-x11-server 21.1.26 · xwayland 24.1.15.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-109904 (X.Org Server XRes QueryClientIds Request Size Overflow), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-109904 (entry last updated 2026-11-13):
Affected:
- X.Org xorg-x11-server: fixed in 21.1.26
- X.Org xwayland: fixed in 24.1.15
Fixed versions: 21.1.26, 24.1.15.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-109904 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-109904 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://gitlab.freedesktop.org/xorg/xserver/-/commit/ff754b812597177412f2e2fa2b1dd1eecbeb75cf
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-109904
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-109904"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- xorg-x11-server
fixed in 21.1.26
- xwayland
fixed in 24.1.15
Evidence 3
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-109904
Is CVE-2026-109904 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-109904?
xorg-x11-server: before 21.1.26. xwayland: before 24.1.15.Source: cve.now feed data
How do I fix CVE-2026-109904?
Upgrade to a fixed version: xorg-x11-server 21.1.26 · xwayland 24.1.15.Source: cve.now feed data