Discourse up to 2026.1.7/2026.6.2/2026.7.1/2026.7.x Post Sanitizer input validation

CVSS Meta Temp Score
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CTI Interest Score
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5.7$0-$5k0.00+

Summaryinfo

A vulnerability, which was classified as critical, was found in Discourse up to 2026.1.7/2026.6.2/2026.7.1/2026.7.x. The impacted element is an unknown function of the component Post Sanitizer. The manipulation results in input validation. This vulnerability is cataloged as CVE-2026-91134. The attack may be launched remotely. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Discourse up to 2026.1.7/2026.6.2/2026.7.1/2026.7.x. It has been classified as critical. Affected is some unknown functionality of the component Post Sanitizer. The manipulation with an unknown input leads to a input validation vulnerability. CWE is classifying the issue as CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the Discourse post sanitizer allowed a stored cross-origin iframe to bypass the allowed_iframes prefix policy when the iframe src contained encoded userinfo. The sanitizer validated a decoded form differently from the stored iframe src, allowing the browser to interpret an attacker-controlled host while the allowlist check accepted the encoded URL as an allowed prefix. An authenticated user with posting privileges could persist the iframe in a post and cause attacker-controlled cross-origin content to be rendered. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-91134 since 09/14/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The technical details are unknown and an exploit is not available.

Upgrading to version 2026.1.8, 2026.6.3, 2026.7.2 or 2026.8.0 eliminates this vulnerability.

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Productinfo

Type

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.9
VulDB Meta Temp Score: 5.7

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 5.4
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: Input validation
CWE: CWE-20
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 2026.1.8/2026.6.3/2026.7.2/2026.8.0

Timelineinfo

09/14/2026 CVE reserved
09/24/2026 +10 days Advisory disclosed
09/24/2026 +0 days VulDB entry created
09/24/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: github.com
Status: Confirmed

CVE: CVE-2026-91134 (🔒)
GCVE (CVE): GCVE-0-2026-91134
GCVE (VulDB): GCVE-100-409614

Entryinfo

Created: 09/24/2026 19:40
Changes: 09/24/2026 19:40 (64)
Complete: 🔍
Cache ID: 216::103

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Discussion

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