---
id: "CVE-2026-113583"
kind: "vulnerability"
aliases: ["CVE-2026-113583"]
title: "Cypht webmail: crafted email image alt text runs script in session"
severity: "medium"
cvss: 6.1
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["cypht", "package", "self-hosted", "webmail"]
not_affected_if: ["default-config", "external-images-disabled"]
published_at: "2026-10-20T12:17:29+00:00"
first_seen_at: "2026-10-23T21:57:20+00:00"
updated_at: "2026-10-25T04:04:13+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-113583", "first_seen_at": "2026-10-23T21:57:20+00:00"}]
---

# Cypht webmail: crafted email image alt text runs script in session

Cypht webmail versions 2.0.0 through 2.12.2 build a blocked-image notice with innerHTML from values taken out of an HTML email. A crafted email can make the victim's browser run attacker JavaScript inside their logged-in session, which can read mail, send mail, or change settings.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed Cypht version in the deployment's release or package metadata, looking for versions from `2.0.0` through `2.12.2`.
- Check whether `ALLOW_EXTERNAL_IMAGE_SOURCES` is enabled in the Cypht configuration.

## Fix

- Upgrade Cypht to a release newer than `2.12.2`; the sources do not name the fixed version.
- Until patched, leave `ALLOW_EXTERNAL_IMAGE_SOURCES` disabled; the sources do not say whether that fully blocks the flaw.

## Timeline

- 2026-10-23T21:57:20+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-113583

## From the sources

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.

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