MongoBleed Unauthenticated Memory Leak

Byadmblake

What is the Vulnerability? A critical vulnerability in MongoDB Server’s handling of zlib-compressed network traffic allows a fully unauthenticated remote attacker to read uninitialized heap memory and leak sensitive data directly from server memory. The flaw stems from improper buffer length handling during zlib decompression. By sending specially crafted malformed packets, an attacker can cause…

What is the Vulnerability?

A critical vulnerability in MongoDB Server’s handling of zlib-compressed network traffic allows a fully unauthenticated remote attacker to read uninitialized heap memory and leak sensitive data directly from server memory.

The flaw stems from improper buffer length handling during zlib decompression. By sending specially crafted malformed packets, an attacker can cause MongoDB to return memory contents beyond intended boundaries, exposing fragments of sensitive in-process data.

Because exploitation occurs before authentication, any MongoDB instance with its network port exposed is vulnerable, significantly increasing real-world attack surface and risk.

A functional proof-of-concept exploit is publicly available and has already been leveraged by attackers, as real-world exploitation has been observed, and CISA has added this vulnerability to its Known Exploited Vulnerabilities (KEV) Catalog, based on evidence of active exploitation.

What is the recommended Mitigation?

  • Patch MongoDB servers to versions:

    8.2.3+, 8.0.17+, 7.0.28+, 6.0.27+, 5.0.32+, 4.4.30+

  • Disable zlib compression if patching cannot yet occur.

  • Restrict internet exposure of MongoDB instances.

  • Post-Exploit Mitigation

    – Rotate all potentially exposed credentials and secrets

    – Review logs for indicators of compromise, including unusual pre-auth requests

    – Monitor public exploit artifacts (e.g., GitHub PoC repos) and network scans

What FortiGuard Coverage is available?

  • FortiGuard Labs is actively monitoring this threat activity and will continue to provide updates as the situation evolves, including new intelligence, indicators, and protection guidance. Meanwhile, it strongly recommends users apply patches as provided by MongoDB.

  • FortiGuard Web Filtering Service protects against malicious URLs, domains, IPs, and other attacker-controlled infrastructure.

  • FortiAnalyzer, FortiSIEM, and FortiSOAR leverage known Indicators of Compromise (IoCs) delivered through the IoC Service to enhance threat hunting, detection, and automated response against related threat activity. FortiGuard Labs continues to monitor for newly emerging IoCs to ensure proactive protection.

  • Organizations suspecting a compromise can contact the FortiGuard Incident Response team for rapid investigation and remediation support.

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