Denial of service in Fluent Bit

1) Input validation error

EUVDB-ID: #VU49224

Risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2019-9749

CWE-ID: CWE-20 - Improper input validation

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to insufficient validation of user-supplied input in the MQTT input plugin in Fluent Bit. 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.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Fluent Bit: 1.0.0 - 1.0.4

CPE2.3

• cpe:2.3:a:fluentbit.io:fluentbit:1.0.0:*:*:*:*:*:*:*
• cpe:2.3:a:fluentbit.io:fluentbit:1.0.1:*:*:*:*:*:*:*
• cpe:2.3:a:fluentbit.io:fluentbit:1.0.2:*:*:*:*:*:*:*

External links

https://github.com/fluent/fluent-bit/issues/1135

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.