A security vulnerability has been detected in NousResearch hermes-agent up to 2026.4.30. Affected is the function GatewayStreamConsumer._filter_and_accumulate of the file gateway/stream_consumer.py of the component Streaming Reasoning Tag Filter. The manipulation leads to improper handling of case sensitivity. The attack may be initiated remotely. The attacks complexity is rated as high. The exploitability is told to be difficult. The exploit has been disclosed publicly and may be used. The project decided to not implement a dedicated fix: [T]he analysis and the fix are both sound. It just lands below the bar for the maintenance cost of a duplicated scrub path.
Weakness
The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.
Extended Description
Improperly handled case sensitive data can lead to several possible consequences, including:
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
References
- https://gist.github.com/YLChen-007/2229e5505bcbb3e15a7ae8fba4c4be37
- https://github.com/NousResearch/hermes-agent/
- https://github.com/NousResearch/hermes-agent/issues/27288
- https://github.com/NousResearch/hermes-agent/pull/28631#issuecomment-4622188016
- https://vuldb.com/cve/CVE-2026-14617
- https://vuldb.com/submit/844654
- https://vuldb.com/vuln/376134
- https://vuldb.com/vuln/376134/cti
- https://vuldb.com/submit/844654