SSRF in Posthog
CVE-2025-1521
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.
Vulnerability class: SSRF (Server-Side Request Forgery)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.007 (49.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 49.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.007 · change: +0.000
Affected products
- Posthog — versions b8817c14065c23159dcf52849f0bdcd12516c43e
Weakness classification (CWE)
Public proof-of-concept exploits
References
- www.zerodayinitiative.com/advisories/ZDI-25-096/ (x_research-advisory, Third Party Advisory)
- github.com/PostHog/posthog/commit/6e8f035f9acd339c5ba87ba6ea40fc1ab3053d42 (vendor-advisory, Patch)
Frequently asked questions
- What is CVE-2025-1521?
- CVE-2025-1521 is a medium-severity vulnerability in Posthog, classified under Server-Side Request Forgery (SSRF). CVSS score: 6.5/10. Published 2025-04-23.
- How severe is CVE-2025-1521?
- Medium severity. CVSS v3 base score is 6.5 out of 10.
- Is CVE-2025-1521 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.