CVE-2026-56139 Apache Camel-Undertow: The muteException consumer option defaulted to false, so a processing error returned the full Java stack trace in the HTTP response body

What is CVE-2026-56139?

CVE-2026-56139 is a medium-severity vulnerability in Apache Camel, published on 6 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Generation of Error Message Containing Sensitive Information vulnerability in Apache Camel Undertow Component.

The camel-undertow HTTP server consumer exposes a muteException option that controls what is returned to the client when a route processing error occurs. This option defaulted to false, whereas the other Camel HTTP server components (camel-http / camel-jetty / camel-servlet and camel-platform-http) default it to true. With muteException=false, when a request triggers an exception during route processing the consumer writes the full Throwable stack trace into the HTTP response body as text/plain instead of returning an empty body. Any unauthenticated client that can reach the endpoint and cause a processing error - for example by sending a malformed request body, an invalid parameter, or otherwise triggering a route-internal failure - therefore receives a complete Java stack trace. Such a stack trace can disclose sensitive internal information, including credentials embedded in exception messages, internal host names and IP addresses, filesystem paths, dependency and version details, database and class names, and the application's internal structure, which an attacker can use to plan further attacks. In addition, for Rest DSL consumers the muteException option was not honoured at all: the RestUndertowHttpBinding was created with a hard-coded false, so the stack trace was returned even when muteException=true had been configured. 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. For deployments that cannot upgrade immediately, set muteException=true explicitly on the camel-undertow consumer (for example undertow: http://0.0.0.0:8080/api?muteException=true , or globally via the camel.component.undertow.mute-exception=true property), so that processing errors no longer return the stack trace to the client; note that on affected releases this workaround does not cover Rest DSL consumers, whose binding ignores the option until the fix is applied.

Weakness: CWE-209

Which versions are affected by CVE-2026-56139?

6 open source packages ship an affected version, including org.apache.camel:camel-undertow. It affects 1 product.

Products include Apache Camel.

How do I fix CVE-2026-56139?

Upgrade org.apache.camel:camel-undertow to a fixed version for your release line: 4.14.8, 4.18.3 or 4.21.0.

Is CVE-2026-56139 being exploited?

There is no known exploitation of CVE-2026-56139 in the wild and no public exploit code.

Public exploit code: 1 proofs of concept on GitHub.

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All Apache Camel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-hjg2-f45w-c566.