Discourse up to 2026.1.5/2026.5.1/2026.6.0 color_scheme_id/dark_scheme_id cross site scripting

CVSS Meta Temp Score
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CTI Interest Score
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6.7$0-$5k0.00+

Summaryinfo

A vulnerability, which was classified as problematic, was found in Discourse up to 2026.1.5/2026.5.1/2026.6.0. This affects an unknown function. The manipulation of the argument color_scheme_id/dark_scheme_id results in cross site scripting. This vulnerability is cataloged as CVE-2026-55674. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in Discourse up to 2026.1.5/2026.5.1/2026.6.0. It has been classified as problematic. Affected is some unknown functionality. The manipulation of the argument color_scheme_id/dark_scheme_id with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. This is going to have an impact on integrity. CVE summarizes:

Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, an unauthenticated attacker could send a single request with a crafted color_scheme_id (or dark_scheme_id) cookie to inject arbitrary HTML into a Discourse page. Because the cookie value was rendered into a color scheme tag without escaping, the attacker could break out of the attribute and inject a tag that bypassed Discourse's nonce-based Content Security Policy, resulting in arbitrary JavaScript execution in visitors' browsers. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-55674 since 06/17/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.007.

Upgrading to version 2026.1.6, 2026.5.2, 2026.6.1 or 2026.7.0 eliminates this vulnerability.

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Type

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.8
VulDB Meta Temp Score: 6.7

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 9.3
CNA Vector (GitHub_M): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Cross site scripting
CWE: CWE-79 / CWE-94 / CWE-74
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Discourse 2026.1.6/2026.5.2/2026.6.1/2026.7.0

Timelineinfo

06/17/2026 CVE reserved
08/17/2026 +61 days Advisory disclosed
08/17/2026 +0 days VulDB entry created
08/17/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: github.com
Status: Confirmed

CVE: CVE-2026-55674 (🔒)
GCVE (CVE): GCVE-0-2026-55674
GCVE (VulDB): GCVE-100-391344

Entryinfo

Created: 08/17/2026 18:50
Changes: 08/17/2026 18:50 (64)
Complete: 🔍
Cache ID: 216::103

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