CVE-2026-33558
MEDIUMCVE-2026-33558 is a medium-severity (CVSS 5.3) vulnerability in org.apache.kafka:kafka-clients. O3 Security confirms whether CVE-2026-33558 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Apache Kafka, Apache Kafka Clients: Information Exposure Through Network Client Log Output
Blast Radius
org.apache.kafka:kafka-clients☕org.apache.kafka:kafka-clientsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Information exposure vulnerability has been identified in Apache Kafka.
The NetworkClient component will output entire requests and responses information in the DEBUG log level in the logs. By default, the log level is set to INFO level. If the DEBUG level is enabled, the sensitive information will be exposed via the requests and responses output log. The entire lists of impacted requests and responses are:
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AlterConfigsRequest
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AlterUserScramCredentialsRequest
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ExpireDelegationTokenRequest
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IncrementalAlterConfigsRequest
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RenewDelegationTokenRequest
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SaslAuthenticateRequest
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createDelegationTokenResponse
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describeDelegationTokenResponse
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SaslAuthenticateResponse
This issue affects Apache Kafka: from any version supported the listed API above through v3.9.1, v4.0.0. We advise the Kafka users to upgrade to v3.9.2, v4.0.1, or later to avoid this vulnerability.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.kafka:kafka-clients | ≥ 0.11.0&&< 3.9.2 | 3.9.2 |
| ☕Maven | org.apache.kafka:kafka-clients | ≥ 4.0.0&&< 4.0.1 | 4.0.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.kafka:kafka-clients. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.apache.kafka:kafka-clients to 3.9.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33558 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-33558 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-33558. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-33558 in your dependencies?
O3 detects CVE-2026-33558 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.