What’s Vulnerable › Vulnerabilities

CVE-2026-113583: Cypht 2.0.0 through 2.12.2 Stored DOM XSS via externalResources.js

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-20 · updated 2026-10-22
• Weakness: CWE-79

Description

Cypht webmail 2.0.0 through 2.12.2 contains a DOM-based cross-site scripting vulnerability that allows remote attackers to execute arbitrary JavaScript by crafting malicious alt text or URL values in an HTML email's external image tag when ALLOW_EXTERNAL_IMAGE_SOURCES is enabled. Attackers can send a specially crafted email so that when the victim opens it, the externalResources.js code builds the blocked-image notice using innerHTML with decoded email-derived values, triggering script execution in the victim's authenticated session to read mailboxes, send email, or change settings.

Affected products

• cypht-org cypht: from 2.0.0 before 2.13.0 — fixed in 2.13.0

How to fix

Upgrade to a fixed version: cypht-org cypht 2.13.0. Check the vendor advisory for mitigations.

References

• https://github.com/cypht-org/cypht/pull/2118/changes/75d2fb83d228be2aaa37036a11eea68d82122d85
• https://github.com/cypht-org/cypht/releases#release-v2.13.0
• https://www.vulncheck.com/advisories/cypht-through-stored-dom-xss-via-externalresources-js

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