CVE-2026-53561: Apache Hive SAML Flaw Affects 4.0.0-4.2.0

The cybersecurity landscape faces a critical advisory regarding Apache Hive with the disclosure of CVE-2026-53561. This vulnerability targets the optional SAML 2.0 authentication framework implemented over HTTP transports in HiveServer2, creating a severe flaw where forged validation tokens can be accepted as legitimate active sessions.

According to official records, affected deployments include Apache Hive versions 4.0.0 up to 4.2.0, along with unreleased branches. The vulnerability stems from a weakness in the validation logic when JDBC or ODBC drivers present a short-term Authorization: Bearer token to the HiveServer2 /cliservice HTTP endpoint. Instead of properly validating the token, the system permitted forged parameters to initialize sessions under arbitrary usernames.

Stock photo for illustration only, not from the actual event

Crucially, exploitation requires no internal Hive credentials, IdP logins, or knowledge of the server signing secret. Network reachability to the HTTP port—including traversal through reverse proxies such as Apache Knox forwarding unauthenticated traffic—is sufficient to execute the attack. Andrew Rukin from Arenadata discovered and reported the bypass, leading to public disclosure on August 25, 2026.

While this issue constitutes user impersonation rather than direct remote code execution, an attacker gains a HiveServer2 session with all privileges associated with the targeted username. Furthermore, the 4.2.1 update bundles fixes for two sibling vulnerabilities discovered in the same code train: a Metastore default-on SQL injection and an Avro SerDes remote schema fetch issue.