What is CVE-2026-113583?

CVE-2026-113583 is a medium-severity vulnerability in Cypht-Org Cypht, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-10-20.

How severe is CVE-2026-113583?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in Cypht-Org Cypht

CVE-2026-113583

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.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2026-10-20.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Cypht-Org Cypht

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

github.com/cypht-org/cypht/pull/2118/changes/75d2fb83d228be2aaa37036a11eea68d82… (issue-tracking)
github.com/cypht-org/cypht/releases (patch)
www.vulncheck.com/advisories/cypht-through-stored-dom-xss-via-externalresources… (third-party-advisory)

Frequently asked questions

What is CVE-2026-113583?: CVE-2026-113583 is a medium-severity vulnerability in Cypht-Org Cypht, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-10-20.
How severe is CVE-2026-113583?: Medium severity. CVSS v3 base score is 6.1 out of 10.