CVE
X.Org xwayland stack buffer overflow in XTestFakeInput valuator handling
Affects xwayland before 24.1.15 and xorg-x11-server before 21.1.26 when a high-axis device and a crafted XTestFakeInput request are involved. Fixed in xwayland 24.1.15 and xorg-x11-server 21.1.26.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in xwayland 24.1.15 · xorg-x11-server 21.1.26
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. A high-axis device and a crafted XTestFakeInput request are needed to trigger the write past the array.
- 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? →
- 14/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- 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 its xwayland component contain a stack buffer overflow in how the XTestFakeInput request handles device valuator data. A local attacker who has low-privilege login access to the system can exploit it to crash the X server or possibly run code in it.
Read the original description
A stack buffer overflow in ProcXTestFakeInput DeviceValuator handling in X.Org xwayland before 24.1.15 and X server before 21.1.26 could be used by authenticated clients to crash or execute code in the X server.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure5/25Specific setups only
- Reach?/20Unknown. No tracked technology or package matched
- Severity8.5/10CVSS 8.5
- No patch0/5No signal
What would change the score
- Would score about 64 if added to CISA KEV
- Would score about 59 if CISA's SSVC rates exploitation active
- Would score about 24 if CISA's SSVC rates it automatable
What to do
Check whether your setup matches what the bug needs.
A high-axis device and a crafted XTestFakeInput request are needed to trigger the write past the array.Upgrade to a fixed version: xwayland 24.1.15 · xorg-x11-server 21.1.26.
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-2026-109093 (X.Org Server XTestFakeInput Valuator Stack Out-Of-Bounds Write), 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-2026-109093 (entry last updated 2026-11-13):
Affected:
- X.Org xwayland: fixed in 24.1.15
- X.Org xorg-x11-server: fixed in 21.1.26
Fixed versions: 24.1.15, 21.1.26.
Conditions (all must be true for the bug to be hit):
- A high-axis device and a crafted XTestFakeInput request are needed to trigger the write past the array. (source: https://gitlab.freedesktop.org/xorg/xserver/-/commit/99ce069ae814b39048543062e073320f14723ee0)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: local access, low-privilege login, no user action.
CISA KEV: CVE-2026-109093 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-109093 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/99ce069ae814b39048543062e073320f14723ee0
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-2026-109093
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-2026-109093"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- xwayland
fixed in 24.1.15
- xorg-x11-server
fixed in 21.1.26
Evidence 2
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-109093
Is CVE-2026-109093 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
What does this mean?
A crafted XTestFakeInput request sent with a high-axis device can make the X server write past the end of an array in the valuator stack. The advisory describes this as an out-of-bounds write.Source: gitlab.freedesktop.org
Which versions are affected by CVE-2026-109093?
xwayland: before 24.1.15. xorg-x11-server: before 21.1.26.Source: cve.now feed data
Am I affected, and how do I check?
The listed ranges cover xwayland before 24.1.15 and xorg-x11-server before 21.1.26. Triggering the write requires a high-axis device and a crafted request, so compare the installed package version against these fixed versions to see where a system falls.Source: gitlab.freedesktop.org
How do I fix CVE-2026-109093?
Upgrade xwayland to 24.1.15 or later and xorg-x11-server to 21.1.26 or later. The sources do not name vendor patch identifiers for this issue.Source: gitlab.freedesktop.org