CVE-2025-1521Network attack vector

Authenticated internal-data disclosure via Slack webhook SSRF

Published Apr 23, 2025 · Updated Apr 23, 2025

Server-side request forgery in PostHog allows remote authenticated users to read sensitive internal data through a crafted Slack webhook URL. The slack_incoming_webhook path passes a user-controlled URL to trackedFetch, whose pre-fix DNS safety check was not bound to the address used by node-fetch, enabling DNS rebinding to an internal address. A valid account with access to configure the Slack webhook is required, and the request runs with the server's network reach and service-account access.

CVSS severity7.1
High
EPSS probability0.61%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Server-side request forgery in PostHog allows remote authenticated users to read sensitive internal data through a crafted Slack webhook URL. The slack_incoming_webhook path passes a user-controlled URL to trackedFetch, whose pre-fix DNS safety check was not bound to the address used by node-fetch, enabling DNS rebinding to an internal address. A valid account with access to configure the Slack webhook is required, and the request runs with the server's network reach and service-account access.

The record

CVE
CVE-2025-1521
Published
Apr 23, 2025
Updated
Apr 23, 2025
Vendor
PostHog
Product
PostHog
Classifications
CWE-918, CAPEC-664, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 23, 2025CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=b8817c14065c23159dcf52849f0bdcd12516c43e

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

PostHog · PostHogversion=b8817c14065c23159dcf52849f0bdcd12516c43e

Published CVSS scores

7.1Zero Day InitiativeCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A: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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
CAPEC-664Server Side Request Forgery
T1190Exploit Public-Facing Application

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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