RCE in Discourse
CVE-2026-55420
Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, under certain non-default configurations, processing of PDF uploads could be exploited to obtain RCE on the server. This issue is patched in 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.
Vulnerability class: Command Injection (OS Command Injection)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.006 (47.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 47.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000
Affected products
- Discourse — versions >= 2026.5.0-latest, < 2026.5.1, >= 2026.4.0-latest, < 2026.4.2, 2026.6.0
Weakness classification (CWE)
References
- github.com/discourse/discourse/security/advisories/GHSA-7wq5-jgww-5rw3 (Mitigation, Vendor Advisory)
- github.com/discourse/discourse/commit/ca5a7e06167561928556afa2f237d67e459c6914 (Patch)
- github.com/discourse/discourse/releases/tag/v2026.1.5 (Release Notes)
- github.com/discourse/discourse/releases/tag/v2026.4.2 (Release Notes)
- github.com/discourse/discourse/releases/tag/v2026.5.1 (Release Notes)
- github.com/discourse/discourse/releases/tag/v2026.6.0 (Release Notes)
Frequently asked questions
- What is CVE-2026-55420?
- CVE-2026-55420 is a high-severity vulnerability in Discourse, classified under OS Command Injection. CVSS score: 7.5/10. Published 2026-07-09.
- How severe is CVE-2026-55420?
- High severity. CVSS v3 base score is 7.5 out of 10.