CVE-2026-46457: Apache Camel: Camel-NATS: Inbound NATS message headers are mapped into the Exchange without a configured HeaderFilterStrategy, allowing a client that can publish to the subject to inject Camel control headers

[Andrea Cosentino <acosentino () apache org>]

Severity: moderate 

Affected versions:

- Apache Camel (org.apache.camel:camel-nats) 4.0.0 before 4.14.8
- Apache Camel (org.apache.camel:camel-nats) 4.15.0 before 4.18.3
- Apache Camel (org.apache.camel:camel-nats) 4.19.0 before 4.21.0

Description:

Improper Input Validation vulnerability in Apache Camel NATS component.

The camel-nats component maps inbound NATS message headers into the Camel Exchange but defaulted its 
headerFilterStrategy to a bare new DefaultHeaderFilterStrategy() with no inbound rules configured (NatsConfiguration). 
With no inFilter, inFilterPattern or inFilterStartsWith set, DefaultHeaderFilterStrategy.applyFilterToExternalHeaders 
returns not filtered for every header name, so NatsConsumer copies every NATS message header - including Camel-internal 
control headers such as CamelHttpUri, CamelFileName or CamelSqlQuery - unmodified onto the Camel message. A client able 
to publish to the consumed NATS subject can therefore inject arbitrary Camel control headers that influence the 
behaviour of downstream producers in the route (for example redirecting an HTTP producer, changing a file name, or 
overriding a query); the injected headers also persist across internal direct, seda and vm hops. The concrete 
downstream impact depends on which producers the route uses. NATS message headers require NATS 2.2 or later, and the 
issue is reachable without credentials when the NATS server is configured without authentication (the NATS server 
default).
This issue affects Apache Camel: from 4.0.0 before 4.14.8, from 4.15.0 before 4.18.3, from 4.19.0 before 4.21.0.

Users are recommended to upgrade to version 4.21.0, which fixes the issue. If users are on the 4.14.x LTS releases 
stream, then they are suggested to upgrade to 4.14.8. If users are on the 4.18.x releases stream, then they are 
suggested to upgrade to 4.18.3. The fix makes camel-nats default to a dedicated NatsHeaderFilterStrategy that filters 
the Camel header namespace case-insensitively on inbound mapping, so client-supplied Camel* / camel* headers are no 
longer copied into the Exchange. For deployments that cannot upgrade immediately, strip the Camel control headers from 
inbound NATS messages before they reach any downstream producer (for example removeHeaders('Camel*') and 
removeHeaders('camel*') at the start of the route), and enable authentication on the NATS server so that only trusted 
clients can publish to the consumed subject.

Credit:

Yu Bao from PayPal (finder)

References:

https://camel.apache.org/security/CVE-2026-46457.html
https://camel.apache.org/
https://www.cve.org/CVERecord?id=CVE-2026-46457