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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-93405
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-24 18:19:07 UTC
Updated2026-09-24 18:19:07 UTC
DescriptionMailspring 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.

Risk And Classification

Primary CVSS: v3.1 6.1 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Problem Types: CWE-79 | CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
3.1CNADECLARED6.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Foundry376 Mailspring affected < 1.17.0 Not specified

References

ReferenceSourceLinkTags
github.com/Foundry376/Mailspring/pull/2523 [email protected] github.com
github.com/Foundry376/Mailspring/security/advisories/GHSA-px2g-jhg5-c6gh [email protected] github.com
github.com/Foundry376/Mailspring/commit/5728388199666ec0a9a58f693c89c25b... [email protected] github.com
github.com/Foundry376/Mailspring/releases/tag/1.17.0 [email protected] github.com
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