# CVE-2026-55420 — discourse

> As of 2026-07-14, CVE-2026-55420 is a HIGH-severity vulnerability in discourse, CVSS v3.1 7.5, EPSS 0.6% (47.3th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-55420 as of 2026-07-14; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-07-14

## What is 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.

The record classifies CVE-2026-55420 under weakness class [CWE-78](https://intel.threadlinqs.com/cwe/CWE-78). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 95 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.5 — HIGH (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **EPSS (FIRST):** 0.6% probability of exploitation in the next 30 days, higher than 47.3% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 5.6/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-09, last modified 2026-07-14

## Is CVE-2026-55420 being exploited?

It currently carries a trending score of 23 in the Threadlinqs vulnerability feed.

## Affected products and versions

- **discourse**: discourse

## How to fix CVE-2026-55420

The record marks a vendor fix as available for CVE-2026-55420. Patch reference: [https://github.com/discourse/discourse/commit/ca5a7e06167561928556afa2f237d67e459c6914](https://github.com/discourse/discourse/commit/ca5a7e06167561928556afa2f237d67e459c6914). Vendor advisory: [https://github.com/discourse/discourse/security/advisories/GHSA-7wq5-jgww-5rw3](https://github.com/discourse/discourse/security/advisories/GHSA-7wq5-jgww-5rw3). Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

## Threat activity tracking CVE-2026-55420

No threat campaign in the Threadlinqs corpus currently references CVE-2026-55420, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-10-12. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com](https://github.com/discourse/discourse/security/advisories/GHSA-7wq5-jgww-5rw3)

**Other references**

- [github.com](https://github.com/discourse/discourse/commit/ca5a7e06167561928556afa2f237d67e459c6914)
- [github.com (v2026.1)](https://github.com/discourse/discourse/releases/tag/v2026.1.5)
- [github.com (v2026.4)](https://github.com/discourse/discourse/releases/tag/v2026.4.2)
- [github.com (v2026.5)](https://github.com/discourse/discourse/releases/tag/v2026.5.1)
- [github.com (v2026.6)](https://github.com/discourse/discourse/releases/tag/v2026.6.0)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-55420
Full detection coverage and IOCs for threats exploiting CVE-2026-55420 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp