CVE-2026-93405 Mailspring: Stored XSS in attachment quick preview (unsanitized Markdown/DOCX/XLSX conversion)
Remote attackers can execute scripts in Mailspring's preview renderer via malicious attachments, potentially leading to code execution.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-93405?
CVE-2026-93405 is a medium-severity cross-site scripting vulnerability in Foundry376 Mailspring, published on 24 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-93405?
How do I fix CVE-2026-93405?
No fix has been published for CVE-2026-93405 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-93405 being exploited?
There is no known exploitation of CVE-2026-93405 in the wild and no public exploit code.
Sources
Also known as GHSA-px2g-jhg5-c6gh.