CVE-2026-13163

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

Published Jun 24, 2026 CVSS 4.0 · 5.3 Medium EPSS < 1% KEV · Not listed
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.

Remediation

Vendor Solution

Upgrade to version 1.0.1 or higher.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Lack of input validation in Mailerup input parameter leads to Open Redirect
First Time appeared Mailerup
Mailerup mailerup
Weaknesses CWE-601
CPEs cpe:2.3:a:mailerup:mailerup:*:*:*:*:*:*:*:*
Vendors & Products Mailerup
Mailerup mailerup
References
Metrics cvssV4_0

{'score': 5.3, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
Secur0
Published
Updated
Jun 24, 2026, 1:07 PM
Reserved
Jun 24, 2026, 12:44 PM
Status
Deferred
Published
Jun 24, 2026, 1:16 PM
Modified
Oct 24, 2026, 1:10 PM