The flaw occurs when a Parquet file supplies a KMS URL that is controlled by the file rather than by application configuration. The Arrow C++ and PyArrow libraries forward that unvalidated URL to a pluggable KmsClient. If the client implementation does not perform host validation, the KMS service token can be transmitted to a malicious host specified by the attacker. This allows the attacker to acquire the KMS authentication token, which can in turn be used to decrypt or otherwise access data protected by that token. The weakness is an improper input validation and a server‑side request forgery scenario, as identified by CWE‑20 and CWE‑918.

Apache Arrow C++ and Apache PyArrow products are affected. All releases from version 4.0.0 through 25.0.1 may forward unvalidated KMS URLs in the absence of application‑controlled settings. Starting with version 26.0.0, the default behavior has been disabled; the feature can only be enabled by explicitly setting the read_kms_url flag in the DecryptionConfiguration.

The CVSS score of 8.1 reflects a high overall risk. The EPSS score is below 1 %, indicating a low probability of active exploitation at this time. The vulnerability is not listed in the CISA KEV catalog. Attackers would need to supply malicious Parquet files that specify a KMS URL pointing to a host under their control. If a KmsClient does not validate that URL, the attacker can receive the KMS authentication token and thereby gain unauthorized access to KMS‑protected data.