An authenticated user who can manage Pulsar functions can trigger a function that publishes a user‑controlled message to any input topic, bypassing the caller’s produce permission. The Functions Worker publishes the message using its own broker‑client credentials, so the message appears to come from the Worker rather than the original caller. This flaw allows the integrity of data streams to be compromised, as consumers may receive messages that should not be allowed to exist. The likely attack vector is the Functions Worker REST API, based on the description of the endpoint that can be accessed by authenticated callers. The vulnerability is an Authorization issue classified as CWE‑862.

Apache Pulsar versions from 2.0.0-rc1-incubating up to 4.0.13 and from 4.1.0 to 4.2.4 are vulnerable. Users of the 4.0.x line should upgrade to at least 4.0.14, while users of the 4.1.x or 4.2.x lines should upgrade to at least 4.2.5. The current supported releases—4.0.x and 5.0.x—include the fix, but older lines remain susceptible. The issue exists only when authorization is enabled; disabling authorization removes the check entirely.

The CVSS score of 4.9 indicates moderate severity. The EPSS score is not provided in the data, so the exploitation likelihood is uncertain and cannot be quantified. The attack vector is inferred from the description of the REST API endpoint, which an authenticated user can reach to trigger the function. The CVE description does not indicate the presence of an exploit, and the vulnerability is not listed in CISA KEV, suggesting no widely documented exploits as of now. Overall, the risk is moderate, with the main concern being the potential to compromise topic integrity without requiring a running function instance.