CVE-2025-55039: Apache Spark: RPC encryption defaults to unauthenticated AES-CTR mode, enabling man-in-the-middle ciphertext modification attacks

[Holden Karau <holden () apache org>]

Severity: moderate 

Affected versions:

- Apache Spark (org.apache.spark:spark-network-common_2.13) 3.5.0 before 3.5.2
- Apache Spark (org.apache.spark:spark-network-common_2.13) before 3.4.4
- Apache Spark (org.apache.spark:spark-network-common_2.12) 3.5.0 before 3.5.2
- Apache Spark (org.apache.spark:spark-network-common_2.12) before 3.4.4

Description:

This issue affects Apache Spark versions before  3.4.4, 3.5.2 and 4.0.0.



Apache Spark versions before 4.0.0, 3.5.2 and 3.4.4 use an insecure default network encryption cipher for RPC 
communication between nodes.

When spark.network.crypto.enabled is set to true (it is set to false by default), but spark.network.crypto.cipher is 
not explicitly configured, Spark defaults to AES in CTR mode (AES/CTR/NoPadding), which provides encryption without 
authentication.

This vulnerability allows a man-in-the-middle attacker to modify encrypted RPC traffic undetected by flipping bits in 
ciphertext, potentially compromising heartbeat messages or application data and affecting the integrity of Spark 
workflows.


To mitigate this issue, users should either configure spark.network.crypto.cipher to AES/GCM/NoPadding to enable 
authenticated encryption or

enable SSL encryption by setting spark.ssl.enabled to true, which provides stronger transport security.

References:

https://spark.apache.org/
https://www.cve.org/CVERecord?id=CVE-2025-55039