KafkaApplication · Apache
CVE-2026-35554
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 · uneditedA race condition in the Apache Kafka Java producer client’s buffer pool management can cause messages to be silently delivered to incorrect topics. When a produce batch expires due to delivery.timeout.ms while a network request containing that batch is still in flight, the batch’s ByteBuffer is prematurely deallocated and returned to the buffer pool. If a subsequent producer batch—potentially destined for a different topic—reuses this freed buffer before the original network request completes, the buffer contents may become corrupted. This can result in messages being delivered to unintended topics without any error being reported to the producer. Data Confidentiality: Messages intended for one topic may be delivered to a different topic, potentially exposing sensitive data to consumers who have access to the destination topic but not the intended source topic. Data Integrity: Consumers on the receiving topic may encounter unexpected or incompatible messages, leading to deserialization failures, processing errors, and corrupted downstream data. This issue affects Apache Kafka versions ≤ 3.9.1, ≤ 4.0.1, and ≤ 4.1.1. Kafka users are advised to upgrade to 3.9.2, 4.0.2, 4.1.2, 4.2.0, or later to address 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 confidenceA race condition in Apache Kafka's Java producer buffer pool causes ByteBuffer deallocation when batches expire (delivery.timeout.ms) while network requests remain in flight. Subsequent batches can reuse the freed buffer before the original request completes, corrupting data and causing messages to be silently delivered to incorrect topics.
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
>= 2.8.0, < 3.9.2>= 4.0.0, < 4.0.2>= 4.1.0, < 4.1.2CVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Determine Kafka broker versionRun 'kafka-topics.sh --version' or 'kafka-broker-api-versions --bootstrap-server <broker>' to retrieve the exact version stringAffected if The version is lower than 3.9.2, 4.0.2, 4.1.2, or 4.2.0
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Identify Java producer usageReview application code or configuration for use of kafka.javaapi.producer.Producer or the newer org.apache.kafka.clients.producer.KafkaProducer classAffected if Java producer is in use; the vulnerability exists specifically in the Java producer buffer pool implementation
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Check delivery.timeout.ms configurationInspect producer configuration property 'delivery.timeout.ms' - if set to a high value (commonly the default of 120000ms or higher), batches remain in flight longer and the race window increasesAffected if delivery.timeout.ms is configured with a value that allows significant time between batch creation and expiration
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Verify high concurrent request configurationReview 'max.in.flight.requests.per.connection' setting (default is 5); higher values increase concurrent in-flight requests and the probability of buffer reuse race conditionAffected if max.in.flight.requests.per.connection is set to a value greater than 1, allowing multiple requests to be in flight simultaneously
A user is affected if running a Kafka version lower than 3.9.2/4.0.2/4.1.2/4.2.0 while using the Java producer with default or high concurrency settings, particularly when delivery.timeout.ms permits extended in-flight periods.
Generated from the published advisory. Verify against your own configuration.
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 · scoped3.9.24.0.24.1.2
Upgrade Apache Kafka to versions 3.9.2, 4.0.2, 4.1.2, 4.2.0 or later to patch the buffer pool race condition.
3.9.2, 4.0.2, 4.1.2, or 4.2.0 (choose the appropriate version for your current branch)
- 1. Identify the current Apache Kafka client version in use by checking project dependencies or build configuration
- 2. Stop all Kafka producer applications that are currently running
- 3. Update the Kafka client dependency to version 3.9.2, 4.0.2, 4.1.2, or 4.2.0 (or later) in your build configuration (Maven pom.xml, Gradle build.gradle, or similar)
- 4. Rebuild and restart the producer applications
- 5. Monitor producer behavior after upgrade to confirm messages are delivered to the correct topics
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Kafka
Scoped from the published advisory
- Consultation4.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-35554 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-35554 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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