CVE-2026-41727

Spring for Apache Kafka: Improper Validation of Retry Topic Header Values Leads to Retry Sequence Manipulation

Spring Kafka's retry topic infrastructure did not sufficiently validate user-controlled header values before acting on them. A producer could send a record with a crafted retry_topic-attempts header to supply an out-of-range attempt count and cause the retry topic router to misidentify where the message was in the retry sequence.

Affected versions:
Spring for Apache Kafka 4.0.0 through 4.0.5; 3.3.0 through 3.3.15; 3.2.0 through 3.2.13; 2.9.0 through 2.9.13; 2.8.0 through 2.8.11.

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

CVE-2026-41727 has a CVSS score of 6.5 (Medium). The vector is network-reachable, low 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 (4.0.6, 3.3.16); upgrading removes the vulnerable code path.

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1. What is CVE-2026-41727? CVE-2026-41727 is a medium-severity improper input validation vulnerability in org.springframework.kafka:spring-kafka (maven), affecting versions >= 4.0.0, <= 4.0.5. It is fixed in 4.0.6, 3.3.16. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
2. How severe is CVE-2026-41727? CVE-2026-41727 has a CVSS score of 6.5 (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 org.springframework.kafka:spring-kafka are affected by CVE-2026-41727? org.springframework.kafka:spring-kafka (maven) versions >= 4.0.0, <= 4.0.5 is affected.
4. Is there a fix for CVE-2026-41727? Yes. CVE-2026-41727 is fixed in 4.0.6, 3.3.16. Upgrade to this version or later.
5. Is CVE-2026-41727 exploitable, and should I be worried? Whether CVE-2026-41727 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-2026-41727 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-2026-41727?
   • Upgrade org.springframework.kafka:spring-kafka to 4.0.6 or later
   • Upgrade org.springframework.kafka:spring-kafka to 3.3.16 or later

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