kafka-python prior to 2.3.2 contains a denial-of-service vulnerability in SCRAM authentication handling that allows a malicious or machine-in-the-middle broker to freeze the client event loop by supplying an excessively large iteration count. In scram.py, ScramClient.process_server_first_message() passes the broker-controlled SCRAM iteration count directly to hashlib.pbkdf2_hmac() without validation, blocking producer sends, consumer polls, admin operations, and heartbeats, which can cause consumer group eviction and repeated reconnect failures.
https://www.vulncheck.com/advisories/kafka-python-prior-to-dos-via-scram-iteration-count-in-scram-py
https://github.com/dpkp/kafka-python/pull/3026
https://github.com/dpkp/kafka-python/pull/3019
https://github.com/dpkp/kafka-python/commit/6e4831444f972d169cdd11f5c8d50333cea3f19b
Published: 2026-06-10
Updated: 2026-06-11
Base Score: 7.8
Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C
Severity: High
Base Score: 7.5
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Severity: High
Base Score: 8.7
Vector: 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
Severity: High
EPSS: 0.00069