CVE-2026-6335Network attack vector

Browser code execution via improper Markdown sanitization

Published May 14, 2026 · Updated May 14, 2026

Cross-site scripting in GitLab CE/EE 18.11 before 18.11.3 allows remote authenticated users to execute code in another user's browser. The Banzai Markdown sanitizer fails to neutralize attacker-controlled content before rendering it as HTML. Exploitation requires authenticated access and user interaction; successful attacks run code in the victim's browser security context.

CVSS severity5.4
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in GitLab CE/EE 18.11 before 18.11.3 allows remote authenticated users to execute code in another user's browser. The Banzai Markdown sanitizer fails to neutralize attacker-controlled content before rendering it as HTML. Exploitation requires authenticated access and user interaction; successful attacks run code in the victim's browser security context.

The record

CVE
CVE-2026-6335
Published
May 14, 2026
Updated
May 14, 2026
Vendor
GitLab
Product
GitLab
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 14, 2026CVE publishedPublication date reported by the CVE source.
  2. May 14, 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=18.11 <18.11.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

GitLab · GitLabversion=18.11 <18.11.3

Published CVSS scores

5.4GitLab Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

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.

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

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript/JScript

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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