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KafkaApplication · Apache

CVE-2026-33558

MEDIUM · 5.3 CVSS v3.1 Published 2026-04-20
Fix available
A fix is available. Upgrade to 3.9.2 or later.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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: * AlterConfigsRequest * AlterUserScramCredentialsRequest * ExpireDelegationTokenRequest * IncrementalAlterConfigsRequest * RenewDelegationTokenRequest * SaslAuthenticateRequest * createDelegationTokenResponse * describeDelegationTokenResponse * 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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Apache Kafka's NetworkClient logs entire request/response payloads at DEBUG level, exposing sensitive authentication credentials (SASL, SCRAM passwords, delegation tokens) in plaintext when DEBUG logging is enabled. Nine request/response types containing authentication secrets are affected.

MitigationUpgrade Apache Kafka to v3.9.2, v4.0.1, or later to receive the fix that prevents logging sensitive credential data. Alternatively, ensure DEBUG logging is disabled (INFO is the default) to avoid exposure.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
KafkaApplication
Affected:>= 0.11.0.0, < 3.9.2= 4.0.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check Apache Kafka version
    Run 'kafka-topics.sh --version' or 'kafka_2.13-version.sh' in the Kafka installation directory, or check the 'kafka_2.13-<version>.jar' filename in the libs folder
    Affected if Version is >= 0.11.0.0 and < 3.9.2, or exactly 4.0.0
  2. Verify DEBUG logging is disabled
    Inspect log4j.properties or logback.xml in the Kafka config directory; look for 'log4j.logger.kafka.network=DEBUG' or similar DEBUG-level appenders for 'kafka.network' or 'kafka.request.logger'
    Affected if DEBUG level is explicitly enabled for network/request loggers (INFO is the default and safe)
  3. Identify if SASL or SCRAM authentication is in use
    Check server.properties for 'sasl.enabled.mechanisms' (SASL) or 'scram.mechanism' settings, or examine JAAS configuration files referenced by 'security.inter.broker.protocol'
    Affected if SASL or SCRAM authentication mechanisms are configured and active

You are affected if running a vulnerable Kafka version AND DEBUG logging is enabled AND SASL/SCRAM authentication is in use, which would expose plaintext credentials in debug logs.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.9.2 or later
Fixed in 3.9.2
Interim mitigation

Upgrade Apache Kafka to v3.9.2, v4.0.1, or later to receive the fix that prevents logging sensitive credential data. Alternatively, ensure DEBUG logging is disabled (INFO is the default) to avoid exposure.

Recommended fix High confidence

3.9.2 or 4.0.1 (or later stable releases)

  1. 1. Identify current Kafka version by checking kafka-topics.sh --version or the jar manifest
  2. 2. Review Kafka release notes for 3.9.2 and 4.0.1 to understand any configuration or compatibility changes
  3. 3. Back up Kafka configuration files (server.properties, log4j.properties, etc.) and data directories
  4. 4. If running in a cluster, plan a rolling upgrade strategy following Kafka upgrade documentation
  5. 5. Upgrade Kafka to version 3.9.2 or 4.0.1 (or later stable release) using your deployment method (package manager, tarball, docker, etc.)
  6. 6. Verify the upgrade by checking that the kafka-topics.sh --version shows the new version
  7. 7. Confirm DEBUG logging no longer outputs sensitive request/response data by reviewing log output
Caveat Review release notes for any breaking changes between your current version and 3.9.2/4.0.1; minor version upgrades within 3.x typically have minimal breaking changes

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Kafka Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-33558 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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