Security readout for executives and security teams
Plain-English summary
Redcarpet versions before 3.5.1 can fail to escape HTML while rendering Markdown quotes, allowing cross-site scripting. The risk matters where untrusted users can submit Markdown that other users view. It is not a server takeover issue in the sources, but it can let attackers alter page content or run script in a victim’s browser.
Executive priority
Treat as a targeted remediation item for applications rendering user-supplied Markdown. Prioritize internet-facing or multi-user platforms first. The issue has a clear fixed version and no cited active exploitation, so urgency is moderate unless sensitive workflows depend on Markdown rendering.
Technical view
CVE-2020-26298 affects vmg redcarpet before 3.5.1. Quote processing did not perform HTML escaping, even with :escape_html enabled. The CVSS 3.1 vector is AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N, consistent with authenticated or low-privilege stored/reflected XSS requiring victim interaction.
Likely exposure
Exposure is likely in Ruby applications that use redcarpet below 3.5.1 to render user-controlled Markdown, such as comments, profiles, issue text, documentation portals, CMS fields, or admin-entered content later viewed in a browser.
Exploitation context
The sources do not report active exploitation, and KEV is false. Exploitation requires Markdown input reaching vulnerable quote rendering and a victim viewing the rendered output. The main documented impact is browser-side script injection affecting content integrity.
Researcher notes
The key detail is that escaping failed specifically during quote processing, including when :escape_html was enabled. Validate exposure by tracing user-controlled Markdown to redcarpet rendering paths and confirming the deployed library version. Avoid assuming other Markdown processors are affected from these sources.
Mitigation direction
- Upgrade redcarpet to version 3.5.1 or later.
- Use patched Debian or Fedora ruby-redcarpet packages where applicable.
- Do not rely on :escape_html in affected versions.
- Check vendor and distribution guidance for supported package-specific fixes.
- Reduce rendering of untrusted Markdown until affected deployments are patched.
Validation and detection
- Inventory application and system packages for redcarpet versions below 3.5.1.
- Review Gemfile.lock and deployed runtime images for bundled redcarpet versions.
- Identify routes that render user-controlled Markdown in browsers.
- Confirm patched versions are present in production after deployment.
- Verify security tests cover Markdown quote rendering with HTML escaping enabled.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-74: Exact CWE lookup
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Open ATT&CK lookupCWE-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2020-26298 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N2.34Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.8MediumVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/advisories/GHSA-q3wr-qw3g-3p4hCVE reference
- https://github.com/vmg/redcarpet/commit/a699c82292b17c8e6a62e1914d5eccc252272793CVE reference
- https://rubygems.org/gems/redcarpetCVE reference
- https://github.com/vmg/redcarpet/blob/master/CHANGELOG.md#version-351-securityCVE reference
- [debian-lts-announce] 20210115 [SECURITY] [DLA 2526-1] ruby-redcarpet security updateCVE reference · mailing-list
- DSA-4831CVE reference · vendor-advisory
- FEDORA-2023-597f13ffb9CVE reference · vendor-advisory
- FEDORA-2023-8682a0e17dCVE reference · vendor-advisory
- FEDORA-2023-44daa9c1d4CVE reference · vendor-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.