# CVE-2026-59303: Spring Cloud Stream unbounded dynamic destination cache

Source: https://junglewise.ai/threats/cve-2026-59303-spring-cloud-stream-unbounded-dynamic-destination-cache  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-27. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-59303 · Severity: low · CVSS 3.1 · Published 2026-08-27

Spring Cloud Stream is a framework used to build event-driven microservices that process streaming data. A flaw in how it manages its destination cache allows an attacker to exhaust memory resources by creating new destinations without limit, potentially causing service availability issues or denial of service.

Vendors: [Spring](https://junglewise.ai/threats/vendors/spring).

## Quick answers

**Is CVE-2026-59303 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-59303 being exploited in the wild.

**How severe is CVE-2026-59303?** Low severity, with a CVSS score of 3.1, published 27 August 2026.

**Which products and versions are affected?** Spring Cloud Stream 4.2.0 - 4.2.6, 4.3.0 - 4.3.3, 5.0.0 - 5.0.2.

**Is there a fix for CVE-2026-59303?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-59303 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-59303?** Check whether you run Spring Cloud Stream at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a resource exhaustion issue in Spring Cloud Stream's dynamic destination cache mechanism. The cache lacks proper size bounds, allowing an attacker to continuously create new destination entries that accumulate in memory without eviction or limits. The attack is network-reachable and requires the ability to send messages with different destination names to a Spring Cloud Stream application. Successful exploitation can lead to memory exhaustion and application unavailability. Patches are available in Spring Cloud Stream 4.2.7+, 4.3.4+, and 5.0.3+.

## Affected products

- Spring Cloud Stream 4.2.0 - 4.2.6, 4.3.0 - 4.3.3, 5.0.0 - 5.0.2

## Timeline

- 2026-08-27: disclosed

## References

- [https://spring.io/security/cve-2026-59303](https://spring.io/security/cve-2026-59303)

## Related threats

- [Spring Cloud Stream deserialization of untrusted types](https://junglewise.ai/threats/cve-2026-59306-spring-cloud-stream-deserialization-of-untrusted-types)