PostHog slack_incoming_webhook Server-Side Request Forgery Information Disclosure Vulnerability

February 25th, 2025
ZDI-25-096 ZDI-CAN-25352

CVE ID

CVE-2025-1521

CVSS Score

7.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N

Affected Vendors

PostHog

Affected Products

PostHog

Vulnerability Details

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.

Additional Details

PostHog has issued an update to correct this vulnerability. More details can be found at:
https://github.com/PostHog/posthog/commit/6e8f035f9acd339c5ba87ba6ea40fc1ab3053d42

Disclosure Timeline

  • 2024-10-03 - Vulnerability reported to vendor
  • 2025-02-25 - Coordinated public release of advisory
  • 2025-02-25 - Advisory Updated

Credit

Mehmet INCE (@mdisec) from PRODAFT.com

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