CVE-2026-88807Network attack vector

Code execution via crafted X server reply

Published Sep 21, 2026 · Updated Sep 21, 2026

Heap-based buffer overflow in X.Org libXrender before 0.9.13 allows remote attackers to inject code via a malicious X server. RenderQueryPictFormats fails to constrain crafted server-reply data to its heap allocation, allowing the reply parser to write beyond the buffer. Exploitation requires an attached X client to connect to the attacker-controlled server and process the malicious reply.

CVSS severity8.9
High
EPSS probability0.26%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in X.Org libXrender before 0.9.13 allows remote attackers to inject code via a malicious X server. RenderQueryPictFormats fails to constrain crafted server-reply data to its heap allocation, allowing the reply parser to write beyond the buffer. Exploitation requires an attached X client to connect to the attacker-controlled server and process the malicious reply.

The record

CVE
CVE-2026-88807
Published
Sep 21, 2026
Updated
Sep 21, 2026
Vendor
The X11 Project
Product
libXrender
Classifications
CWE-122, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <0.9.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The X11 Project · libXrenderversion=0 <0.9.13

Published CVSS scores

8.9GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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