CVE-2025-25294

Fix

Using JSON format as the default format for access logs. The logged document will contain the same key and values as before. Only the order of properties is different inside the logged document.

Workaround

One can overwrite the old text based default format with JSON formatter by setting the following property:
"EnvoyProxy.spec.telemetry.accessLog" to

settings:
- format:
    type: JSON
    json:
      start_time: '%START_TIME%'
      method: '%REQ(:METHOD)%'
      x-envoy-origin-path: '%REQ(X-ENVOY-ORIGINAL-PATH?:PATH)%'
      protocol: '%PROTOCOL%'
      response_code: '%RESPONSE_CODE%'
      response_flags: '%RESPONSE_FLAGS%'
      response_code_details: '%RESPONSE_CODE_DETAILS%'
      connection_termination_details: '%CONNECTION_TERMINATION_DETAILS%'
      upstream_transport_failure_reason: '%UPSTREAM_TRANSPORT_FAILURE_REASON%'
      bytes_received: '%BYTES_RECEIVED%'
      bytes_sent: '%BYTES_SENT%'
      duration: '%DURATION%'
      x-envoy-upstream-service-time: '%RESP(X-ENVOY-UPSTREAM-SERVICE-TIME)%'
      x-forwarded-for: '%REQ(X-FORWARDED-FOR)%'
      user-agent: '%REQ(USER-AGENT)%'
      x-request-id: '%REQ(X-REQUEST-ID)%'
      :authority: '%REQ(:AUTHORITY)%'
      upstream_host: '%UPSTREAM_HOST%'
      upstream_cluster: '%UPSTREAM_CLUSTER%'
      upstream_local_address: '%UPSTREAM_LOCAL_ADDRESS%'
      downstream_local_address: '%DOWNSTREAM_LOCAL_ADDRESS%'
      downstream_remote_address: '%DOWNSTREAM_REMOTE_ADDRESS%'
      requested_server_name: '%REQUESTED_SERVER_NAME%'
      route_name: '%ROUTE_NAME%'

see API definition here

References

Are there any links users can visit to find out more?

In all Envoy Gateway versions prior to 1.2.7 and 1.3.1 a default Envoy Proxy access log configuration is used. This format is vulnerable to log injection attacks.

If the attacker uses a specially crafted user-agent which performs json injection, then he could add and overwrite fields to the access log.

Examples of attacks include:

• Using following string as user agent : HELLO-WORLD", "evil-ip": "1.1.1.1", "x-forwarded-for": "1.1.1.1 would lead to setting of new access log properties and overwrite of existing properties. Existing properties such as the value of the X-Forwarded-For header may have importance for security analysis of access logs, and their overwrite can be used to hide malicious activity.

• Using the following string as user-agent : " which renders an invalid json document. The invalid document may fail to be processed by observability solutions, which would allow attacker to hide malicious activity.

CVE-2025-25294 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.2.7, 1.3.1); upgrading removes the vulnerable code path.

Kodem intelligence

1.3.1, 1.2.7

1. What is CVE-2025-25294? CVE-2025-25294 is a medium-severity security vulnerability in github.com/envoyproxy/gateway (go), affecting versions < 1.2.7. It is fixed in 1.2.7, 1.3.1.
2. How severe is CVE-2025-25294? CVE-2025-25294 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/envoyproxy/gateway are affected by CVE-2025-25294? github.com/envoyproxy/gateway (go) versions < 1.2.7 is affected.
4. Is there a fix for CVE-2025-25294? Yes. CVE-2025-25294 is fixed in 1.2.7, 1.3.1. Upgrade to this version or later.
5. Is CVE-2025-25294 exploitable, and should I be worried? Whether CVE-2025-25294 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-25294 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-25294?
   • Upgrade github.com/envoyproxy/gateway to 1.2.7 or later
   • Upgrade github.com/envoyproxy/gateway to 1.3.1 or later