CVE-2026-13163

MEDIUM

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

Title source: cna

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.

References (1)

Core 1

Core References

Patch patch

https://github.com/Maalfer/mailerup/commit/99eb6d4586134bf3f4422093fbf47d6794ef0ee5

View Patch ZIP pw:eip

Scores

CVSS v4 5.3

EPSS 0.0033

EPSS Percentile 25.4%

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CISA SSVC

Vulnrichment

Exploitation none

Automatable no

Technical Impact partial

Details

CWE

CWE-601

Status published

Products (1)

Mailerup/Mailerup < 1.0.1

Published Jun 24, 2026

Tracked Since Jun 24, 2026