Arcane Backend: Unauthenticated reflected XSS via SVG color parameter enables admin account takeover

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-45627: 0.18% estimated exploitation activity in the next 30 days; percentile 8.12 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The unauthenticated GET /api/app-images/logo endpoint reflects a user-supplied color query parameter into the body of an SVG document via strings.ReplaceAll with no escaping. The substitution lands inside a <style element of the embedded logo.svg, allowing an attacker to close the style block and inject executable <script content. Because the response is served as image/svg+xml and Arcane sets no Content-Security-Policy or X-Content-Type-Options headers, navigating a logged-in admin victim to a crafted URL executes attacker-controlled JavaScript in Arcane's origin and rides the victim's HttpOnly JWT cookie to fully compromise the admin account. Details The route is registered in backend/internal/huma/handlers/appimages.go:53-61 with an explicitly empty security requirement, marking it as public: backend/internal/huma/middleware/auth.go:209-213 honors the empty Security value by returning reqs.isRequired == false and short-circuiting with next(ctx), so no JWT/API-key check…

Published by the source

18 May 2026, 14:19 UTC

Last modified by the source

9 Jun 2026, 10:30 UTC

Source last checked

26 Oct 2026, 15:23 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-q2pj-8v84-9mh5

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# Patch Next advisory brief: CVE-2026-45627

Advisory: Arcane Backend: Unauthenticated reflected XSS via SVG color parameter enables admin account takeover
IDs: CVE-2026-45627, GHSA-q2pj-8v84-9mh5
Record: https://patchnext.com/advisories/cve-2026-45627 (revision 1, source checked 26 Oct 2026, 15:23 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/getarcaneapp/arcane/backend 1.19.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/getarcaneapp/arcane/backend: affected <= 1.18.1; fixed in 1.19.0

## Suggested inspection (read-only)
- Go github.com/getarcaneapp/arcane/backend: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/getarcaneapp/arcane/backend.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-q2pj-8v84-9mh5 (GitHub-reviewed advisory GHSA-q2pj-8v84-9mh5 lists affected ranges: Go github.com/getarcaneapp/arcane/backend >=0 <=1.18.1)

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