VulnerabilityPublished 17 Dec 2025

Inside PostHog: How SSRF, a ClickHouse SQL Escaping 0day, and Default PostgreSQL Credentials Formed an RCE Chain (ZDI-25-099, ZDI-25-097, ZDI-25-096)

Source Reddit NetSec

Severity

Medium

Rated by Threat Radar

Data as of 17 Dec 2025, 19:06 UTC

What to do

AI-suggested

1. Immediately change all default PostgreSQL credentials used by PostHog installations to strong, unique passwords. 2. Apply any available patches or updates to PostHog, ClickHouse, and PostgreSQL as soon as they are released addressing these vulnerabilities. 3. Restrict SSRF attack vectors by implementing strict input validation and network segmentation to limit internal service exposure. 4. Employ Web Application Firewalls (WAFs) with rules targeting SSRF and SQL injection patterns specific to ClickHouse. 5. Conduct thorough audits of database configurations to ensure secure authentication and authorization settings. 6. Monitor logs for unusual SSRF requests, suspicious SQL queries, and authentication anomalies. 7. Use network-level controls to restrict outbound requests from PostHog services to only necessary endpoints. 8. Educate development and operations teams about secure coding practices to prevent SQL injection and credential mismanagement. 9. Consider deploying runtime application self-protection (RASP) tools to detect and block exploitation attempts in real-time. 10. Prepare incident response plans tailored to potential RCE incidents involving analytics platforms.

Description

A critical remote code execution (RCE) vulnerability chain was discovered in PostHog involving Server-Side Request Forgery (SSRF), a zero-day SQL escaping flaw in ClickHouse, and default PostgreSQL credentials. This chain allows attackers to escalate from SSRF to full RCE on the affected system. Although no known exploits are currently in the wild, the combination of these vulnerabilities poses a significant risk. The vulnerabilities stem from improper input validation, insecure default credentials, and SQL injection weaknesses. European organizations using PostHog for analytics or data processing could face data breaches, system compromise, and service disruption. Mitigation requires immediate credential changes, patching or configuration hardening of ClickHouse and PostgreSQL, and restricting SSRF attack vectors. Countries with higher adoption of PostHog and related database technologies, such as Germany, the UK, France, and the Netherlands, are most at risk. Given the ease of exploitation and potential impact on confidentiality, integrity, and availability, this threat is assessed as high severity. Defenders should prioritize detection of SSRF attempts, audit default credentials, and apply security best practices to prevent exploitation.

Impact

For European organizations, the impact of this RCE chain is substantial. PostHog is increasingly adopted by enterprises for product analytics, meaning sensitive user and business data could be exposed. Successful exploitation could lead to unauthorized access to internal systems, data breaches involving personal and corporate information, disruption of analytics services, and potential use of compromised systems as a foothold for further attacks. Given the GDPR regulatory environment, data breaches could result in significant legal and financial penalties. Additionally, organizations relying on ClickHouse and PostgreSQL databases in conjunction with PostHog may face compounded risks due to the interconnected nature of these vulnerabilities. The attack could also undermine trust in analytics platforms and impact operational continuity. The lack of known exploits currently provides a window for proactive defense, but the medium severity rating suggests that exploitation is feasible and impactful enough to warrant immediate attention.

Summary

The reported security threat involves a chained exploitation path within PostHog, an open-source product analytics platform. The chain begins with a Server-Side Request Forgery (SSRF) vulnerability that allows an attacker to make unauthorized internal network requests. Leveraging this SSRF, the attacker exploits a zero-day SQL escaping vulnerability in ClickHouse, a columnar database used by PostHog, which allows injection of malicious SQL commands due to improper escaping of input. This SQL injection is then combined with the presence of default, weak PostgreSQL credentials within the PostHog environment, enabling the attacker to escalate privileges and execute arbitrary code remotely (RCE). The combination of these three vulnerabilities forms a potent attack vector that bypasses typical security controls. The SSRF flaw enables internal network reconnaissance and pivoting, the ClickHouse SQL escaping 0day allows injection of malicious queries, and the default PostgreSQL credentials provide the final foothold for code execution. Although no public exploits have been reported, the technical complexity is moderate, and the impact of successful exploitation includes full system compromise, data exfiltration, and potential lateral movement within the network. The vulnerabilities highlight common security pitfalls such as insecure defaults, insufficient input validation, and inadequate database hardening.

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Description

AI analysisMachine-generated, updated 17 Dec 2025, 19:06 UTC

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