CVE-2026-106440

Hydra from 1.3.4 until 1.3.6 and 1.4.0.dev9 has an incomplete target blacklist for instantiate() that does not fully check the effective callable selected by the target field. Execution wrappers such as timeit.timeit, pickle.loads, aliases, callable-returning helpers, generic dispatch, and deferred calls can obscure or defer the effective target and bypass name-based authorization.

Hydra prior to 1.3.6 and 1.4.0.dev9 passes Python logging configuration to logging.config.dictConfig() without applying Hydra's target policy to handler class values or formatter, filter, handler, queue, and listener factories. An attacker who controls Hydra logging configuration can select an importable class or factory and cause it to be invoked with the application's privileges.

Hydra from 1.3.4 until 1.3.7 and 1.4.0.dev10 stores legacy instantiate target blocklists and related execution-policy collections in mutable module-level state. An attacker who controls multiple sibling target entries can resolve hydra._internal.target_policy.UNCONTROLLED_EXECUTION_TARGETS.discard through instantiate(), remove a denied target, and then invoke that target because sibling nodes are processed in insertion order against the same modified policy.

Hydra before version 1.3.4 has an arbitrary code execution vulnerability. The hydra.utils.instantiate() function resolves and calls Python objects selected by configuration, allowing an attacker to invoke dangerous callables.

A stack buffer overflow vulnerability in Hydra through version 9.7 (fixed in commit 9cc84c2) affects NTLM authentication in SMTP, POP3, IMAP, NNTP, HTTP, HTTP-Proxy, and HTTP-Proxy-Urlenum modules when processing malicious NTLM Type-2 challenges. A remote server can send a crafted challenge with an excessively long domain string, causing base64-encoded response data to overflow a 500-byte stack buffer by 18 to 330 bytes, enabling remote code execution on systems without stack protection.