CVE-2026-13163

Lack of input validation in Mailerup input parameter leads to Open Redirect

State: Published
Severity: 5.3 Medium
Published: Jun 24, 2026
Updated: Jun 24, 2026
Reserved: Jun 24, 2026

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.

Scores

CVSS	Score	Vector	Source
4.0	5.3 Medium	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N	Secur0

Weaknesses

CWE-601 URL redirection to untrusted site ('open redirect')

Affected Products

Product	Versions
MailerupMailerup	before 1.0.1Affected

References

https://github.com/Maalfer/mailerup/commit/99eb6d4586134bf3f4422093fbf47d6794ef0ee5patch

Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.