CVE-2026-13163 Lack of input validation in Mailerup input parameter leads to Open Redirect
Remote attackers can redirect users to malicious sites via crafted parameters in Mailerup, enabling phishing attacks due to missing host validation.
- 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-2026-13163?
CVE-2026-13163 is a medium-severity vulnerability in Mailerup, published on 24 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
Open redirect vulnerability (CWE-601) in the _safe_redirect function of the click-tracking endpoint (/c/<token>/) in Mailerup <1.0.0 on all platforms allows remote unauthenticated attackers to redirect victims to arbitrary external sites and conduct phishing attacks via a crafted u query parameter, because the URL scheme is validated (blocking javascript: and data:) but the destination host is not restricted to an allowlist, and a signing.BadSignature exception is silently caught so a valid signed token is not required.
Weakness: CWE-601
Which versions are affected by CVE-2026-13163?
How do I fix CVE-2026-13163?
No fix has been published for CVE-2026-13163 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-13163 being exploited?
There is no known exploitation of CVE-2026-13163 in the wild and no public exploit code.
Sources
Also known as GHSA-wfgr-g7h2-c6m6.