CVE-2025-1521

CVE-2025-1521 is a medium-severity vulnerability in Posthog with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-918.

Key facts

• Severity: Medium (CVSS 3.x base score 6.5)
• EPSS exploit prediction: 1% (42nd percentile)
• Actively exploited: Not listed in CISA KEV
• EU (EUVD) id: EUVD-2025-12185
• Weakness: CWE-918
• Affected product: Posthog
• Published: 2025-04-23
• Last modified: 2026-06-17

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.

Frequently asked questions

What is 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.

How severe is CVE-2025-1521?

CVE-2025-1521 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2025-1521 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-1521?

CVE-2025-1521 affects Posthog. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-1521?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-1521 have an EU (EUVD) identifier?

Yes. CVE-2025-1521 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-12185.

When was CVE-2025-1521 published?

CVE-2025-1521 was published on 2025-04-23 and last updated on 2026-06-17.

References

• https://github.com/PostHog/posthog/commit/6e8f035f9acd339c5ba87ba6ea40fc1ab3053d42
• https://www.zerodayinitiative.com/advisories/ZDI-25-096/

Affected products (1)

• cpe:2.3:a:posthog:posthog:*:*:*:*:*:*:*:*

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