An issue was discovered in the MQTT input plugin in Fluent Bit through 1.0.4. When this plugin acts as an MQTT broker (server), it mishandles incoming network messages. After processing a crafted packet, the plugin's mqtt_packet_drop function (in /plugins/in_mqtt/mqtt_prot.c) executes the memmove() function with a negative size parameter. That leads to a crash of the whole Fluent Bit server via a SIGSEGV signal.

flb_gzip_compress in flb_gzip.c in Fluent Bit before 1.6.4 has an out-of-bounds write because it does not use the correct calculation of the maximum gzip data-size expansion.

Fluent Bit 1.6.10 has a NULL pointer dereference when an flb_malloc return value is not validated by flb_avro.c or http_server/api/v1/metrics.c.

Fluent Bit (aka fluent-bit) 1.7.0 through 1.7.4 has a double free in flb_free (called from flb_parser_json_do and flb_parser_do).

An issue was discovered in Treasure Data Fluent Bit 1.7.1, erroneous parsing in flb_pack_msgpack_to_json_format leads to type confusion bug that interprets whatever is on the stack as msgpack maps and arrays, leading to use-after-free. This can be used by an attacker to craft a specially craft file and trick the victim opening it using the affect software, triggering use-after-free and execute arbitrary code on the target system.

An issue was discovered in Treasure Data Fluent Bit 1.7.1, a wrong variable is used to get the msgpack data resulting in a heap overflow in flb_msgpack_gelf_value_ext. An attacker can craft a malicious file and tick the victim to open the file with the software, triggering a heap overflow and execute arbitrary code on the target system.

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.

Digdag is an open source tool that to build, run, schedule, and monitor complex pipelines of tasks across various platforms. Treasure Data's digdag workload automation system is susceptible to a path traversal vulnerability if it's configured to store log files locally. This issue may lead to information disclosure and has been addressed in release version 0.10.5.1. Users are advised to upgrade. There are no known workarounds for this vulnerability.

fluent-bit 2.2.2 contains a Use-After-Free vulnerability in /fluent-bit/plugins/custom_calyptia/calyptia.c.

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.

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.

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 cfl_sds_len, which in turn tries to cast a NULL pointer into struct cfl_sds. This is related to process_payload_traces_proto_ng() at opentelemetry_prot.c.

Fluent Bit in_forward input plugin does not properly enforce the security.users authentication mechanism under certain configuration conditions. This allows remote attackers with network access to the Fluent Bit instance exposing the forward input to send unauthenticated data. By bypassing authentication controls, attackers can inject forged log records, flood alerting systems, or manipulate routing decisions, compromising the authenticity and integrity of ingested logs.

The extract_name function in Fluent Bit in_docker input plugin copies container names into a fixed size stack buffer without validating length. An attacker who can create containers or control container names, can supply a long name that overflows the buffer, leading to process crash or arbitrary code execution.

Fluent Bit out_file 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.

Fluent Bit in_http, in_splunk, and in_elasticsearch input plugins fail to sanitize tag_key inputs. An attacker with network access or the ability to write records into Splunk or Elasticsearch can supply tag_key values containing special characters such as newlines or ../ that are treated as valid tags. Because tags influence routing and some outputs derive filenames or contents from tags, this can allow newline injection, path traversal, forged record injection, or log misrouting, impacting data integrity and log routing.

Fluent Bit in_http, in_splunk, and in_elasticsearch input plugins contain a flaw in the tag_key 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.

An issue in fluent-bit v.3.7.2 allows a local attacker to cause a denial of service via the function consume_event.

An issue in fluent-bit v.3.7.2 allows a local attacker to cause a denial of service via the cfl_list_size in cfl_list.h:165.