An issue was discovered in Fluent Bit 3.1.9. When the Prometheus Remote Write input plugin is running and listening on an IP address and port, one can send a packet with Content-Length: 0 and it crashes the server. Improper handling of the case when Content-Length is 0 allows a user (with access to the endpoint) to perform a remote Denial of service attack. The crash happens because of a NULL pointer dereference when 0 (from the Content-Length) is passed to the function cfl_sds_len, which in turn tries to cast a NULL pointer into struct cfl_sds. This is related to process_payload_metrics_ng() at prom_rw_prot.c.

References

• https://nvd.nist.gov/vuln/detail/CVE-2024-50608
• https://fluentbit.io/announcements
• https://github.com/fluent/fluent-bit/releases
• https://www.ebryx.com/blogs/exploring-cve-2024-50608-and-cve-2024-50609