CVE-2026-49294 Valhalla has reflected XSS via unsanitized JSONP callback parameter
Attackers can execute arbitrary JavaScript in victims' browsers via a malicious JSONP callback parameter, potentially stealing sessions or credentials.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-49294?
CVE-2026-49294 is a medium-severity cross-site scripting vulnerability in valhalla, published on 15 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Valhalla is an open source routing engine and accompanying libraries for use with OpenStreetMap data. Versions 3.6.3 and prior are vulnerable to reflected cross-site scripting (XSS) due to improper neutralization of input in the JSONP callback parameter. When a request specifies a JSONP callback, the value is reflected directly into the HTTP response body with Content-Type: application/javascript, without any validation, output encoding, or allowlist filtering. An attacker can craft a URL containing arbitrary JavaScript in the callback parameter; if a victim is induced to load that URL via a <script src="..."> tag, the injected script executes in the context of the serving origin, potentially leading to session token theft, credential disclosure, or actions performed on behalf of the victim. This issue was not fixed at time of publication.
Weakness: CWE-79
Which versions are affected by CVE-2026-49294?
How do I fix CVE-2026-49294?
No fix has been published for CVE-2026-49294 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-49294 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-49294 exists.
Sources
Also known as GHSA-85xx-39j8-r56x.