Discourse: Chat upload filenames rendered as raw HTML in excerpts
CVSS score
5.0
EPSS probability
%0.3
Risk score
0.0
Published
20 d ago
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Impact on My Inventory
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Vulnerability description
DayBreach CVE AI Research
CVE-2026-91121 has vendor, distribution, patch and security-source records on file. We can compare them and prepare an explanation linked to the evidence.
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, attacker-controlled upload filenames used in chat message excerpts were rendered as unescaped HTML. A user able to upload a file and send chat content could place markup in a filename that was then interpreted by chat channel lists, chat summary emails, pinned message bars, reply previews, thread previews, and other excerpt renderers. The issue allowed trusted-HTML injection that altered rendered excerpt content, but JavaScript execution was not demonstrated with default Content Security Policy settings. The advisory states that no confidentiality, integrity, or availability impact was identified, while its structured scoring metadata separately assigns low integrity impact. Sites that disable or relax the default CSP have increased exposure. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
IMPACT: Affected Products and Software
Affected Products
The following products are affected by CVE-2026-91121 vulnerability. Where our threat engine knows the exact affected versions, they are listed below.
| ID | VENDOR | PRODUCT | ACTION |
|---|---|---|---|
| 1 | discourse | discourse | View |
RED HAT CSAF/VEX: Product Impact Check
SCORING: CVSS from Multiple Sources
CVSS Scores
The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.
| SCORE | VERSION | SEVERITY | VECTOR | SOURCE |
|---|---|---|---|---|
| 5.0 | CVSS V31 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N | NVD |
| 5.0 | CVSS V3_1 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N | CVE CNA |
Patch and Remediation Guide
Solution & Remediation Advisory
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Public exploit and active exploitation status
Verified exploit intelligence
No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.
Weakness Classification and Attack Patterns (CWE & CAPEC)
CWE - Common Weakness Enumeration
While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-91121 is associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-91121 weaknesses.
Attack Vector and Accessibility
Official Sources and Advisories
CVSS Vector Radar Chart
5.0 / 10Vulnerability Scoring Details
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:NYama durumu bilinmiyor
Weakness Type (CWE & CAPEC)
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Get this vulnerability through the API
Affected products, version ranges, exploitation status and patch information in a single request, with a free key.
curl -H "x-api-key: $DAYBREACH_API_KEY" \ "https://api.daybreach.dev/api/v1/intel/cves/CVE-2026-91121"