CVE-2025-1521 PostHog slack_incoming_webhook Server-Side Request Forgery Information Disclosure Vulnerability

High 7.1 Published 23 Apr 2025 Updated 23 Apr 2025

Authenticated attackers can exploit SSRF in PostHog's Slack webhook to disclose sensitive information and potentially execute code.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2025-1521?

CVE-2025-1521 is a high-severity server-side request forgery vulnerability in PostHog, published on 23 Apr 2025. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

PostHog slack_incoming_webhook Server-Side Request Forgery Information Disclosure Vulnerability. This vulnerability allows remote attackers to disclose sensitive information on affected installations of PostHog. Authentication is required to exploit this vulnerability.

The specific flaw exists within the processing of the slack_incoming_webhook parameter. The issue results from the lack of proper validation of a URI prior to accessing resources. An attacker can leverage this vulnerability to execute code in the context of the service account. Was ZDI-CAN-25352.

Weakness: CWE-918

Which versions are affected by CVE-2025-1521?

It affects 1 product.

Products include Posthog Posthog.

How do I fix CVE-2025-1521?

No fix has been published for CVE-2025-1521 yet. Limit exposure of the affected software until one is available.

Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.

Is CVE-2025-1521 being exploited?

There is no known exploitation of CVE-2025-1521 in the wild and no public exploit code.

Sources

Also known as GHSA-8w5j-q5mj-5jpv.