CVE-2026-13163

MEDIUM
MEDIUM Priority: 0.03 BB Relevance: 61/100
Published: 2026-06-24 Modified: 2026-10-24 First seen: 2026-10-29 Status: active

Attack Surface

Network Low Complexity No Auth

CVSS Vector Breakdown

AV: Network
AC: Low
PR: None
UI: Passive
S: X
AT: None
VC: None
VI: None
VA: None

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 Classification (1)

Bug Bounty Relevance

61 / 100
✓ Network accessible
✓ No authentication
✓ Low complexity

CVSS Score

5.3 / 10.0 v4.0
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

EPSS — Exploitation Probability

0.51%
Raw Score 0.005100
Percentile 43.4%
Date 2026-10-29

EPSS Trend

2026-10-29
0.00510
2026-10-28
0.00510

Intelligence Sources

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