CVE-2026-13163Network attack vector

Unauthenticated phishing redirects via unrestricted destination hosts

Published Jun 24, 2026 · Updated Jun 24, 2026

Open redirect in Maalfer MailerUp before 1.0.1 allows remote attackers to send victims to external sites through crafted click links. The _safe_redirect function validates the u parameter scheme but does not restrict the destination host, so the click-tracking endpoint returns an external redirect. A valid signed token is unnecessary because signing.BadSignature is silently caught, but a victim must follow the crafted link for phishing redirection.

CVSS severity5.3
Medium
EPSS probability0.51%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Open redirect in Maalfer MailerUp before 1.0.1 allows remote attackers to send victims to external sites through crafted click links. The _safe_redirect function validates the u parameter scheme but does not restrict the destination host, so the click-tracking endpoint returns an external redirect. A valid signed token is unnecessary because signing.BadSignature is silently caught, but a victim must follow the crafted link for phishing redirection.

The record

CVE
CVE-2026-13163
Published
Jun 24, 2026
Updated
Jun 24, 2026
Vendor
Maalfer
Product
MailerUp
Classifications
CWE-601, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <1.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Maalfer · MailerUpversion=0 <1.0.1

Published CVSS scores

5.3Secur0CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-601URL Redirection to Untrusted Site ('Open Redirect')
T1204.001Malicious Link

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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