All vulnerabilities
CVE-2026-93405GHSA-px2g-jhg5-c6gh

Mailspring: Stored XSS in attachment quick preview (unsanitized Markdown/DOCX/XLSX conversion)

Foundry376 Mailspring
Open in ThreatlineRecord JSON
CVSS
6.1Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.22%Chance of exploitation activity in the next 30 days, higher than 12% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in1.17.0Fixed versionGitHub
Published24 Sep 2026Updated 29 Sep 2026CVE List

What fixes it

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

Mailspring is a fast, cross-platform, open-source email client. Prior to 1.17.0, attachment quick preview converts Markdown, DOCX, and XLSX attachments with Snarkdown, Mammoth, and SheetJS and inserts the resulting HTML into the preview document through innerHTML without sanitization. A remote sender can craft a supported attachment whose converted HTML executes script when a recipient opens quick preview. The preview renderer has no direct Node or Electron access, but injected script can reach the IPC surface exposed to the quick-preview renderer. This issue alone provides script execution in the preview renderer; separate path-traversal and renderer-controlled file-write vulnerabilities are required for the documented persistent code-execution chain. This issue is fixed in version 1.17.0.

Text from CVE List

Affected versions 2

  • Mailspringaffected: < 1.17.0CVE List
  • mailspring, other< 1.17.0GitHub

References 4