A memory corruption vulnerability in Fluent Bit versions 2.0.7 thru 3.0.3. This issue lies in the embedded http server’s parsing of trace requests and may result in denial of service conditions, information disclosure, or remote code execution.
CVE-2025-12977
CVE-2025-12970
fluent-bit 2.2.2 contains a Use-After-Free vulnerability in /fluent-bit/plugins/customcalyptia/calyptia.c.
In Fluent Bit 2.1.8 through 2.2.1 a NULL pointer dereference can be caused via an invalid HTTP payload with the content type of x-www-form-urlencoded. It crashes and does not restart. This could result in logs not being delivered properly.
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 cflsdslen, which in turn tries to cast a NULL pointer into struct cflsds. This is related to processpayloadmetricsng() at promrwprot.c.
An issue was discovered in Fluent Bit 3.1.9. When the OpenTelemetry 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 cflsdslen, which in turn tries to cast a NULL pointer into struct cflsds. This is related to processpayloadtracesprotong() at opentelemetryprot.c.
CVE-2025-12969
An issue in fluent-bit v.3.7.2 allows a local attacker to cause a denial of service via the function consumeevent.
An issue in fluent-bit v.3.7.2 allows a local attacker to cause a denial of service via the cfllistsize in cfllist.h:165.
Fluent Bit inhttp, insplunk, and inelasticsearch input plugins contain a flaw in the tagkey validation logic that fails to enforce exact key-length matching. This allows crafted inputs where a tag prefix is incorrectly treated as a full match. A remote attacker with authenticated or exposed access to these input endpoints can exploit this behavior to manipulate tags and redirect records to unintended destinations. This compromises the authenticity of ingested logs and can allow injection of forged data, alert flooding and routing manipulation.
Fluent Bit outfile plugin does not properly sanitize tag values when deriving output file names. When the File option is omitted, the plugin uses untrusted tag input to construct file paths. This allows attackers with network access to craft tags containing path traversal sequences that cause Fluent Bit to write files outside the intended output directory.