# CVE-2026-59299: Spring Cloud Function composition lookup function poisoning

Source: https://junglewise.ai/threats/cve-2026-59299-spring-cloud-function-composition-lookup-function-poisoning  
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-2026-59299 · Severity: low · CVSS 3.1 · Published 2026-08-27

Spring Cloud Function is a framework used to build serverless applications and microservices. A vulnerability in composition lookup allows attackers to potentially poison base functions, which could lead to unexpected behavior, code execution, or disruption of function processing. Organizations using Spring Cloud Function for critical services may experience service degradation or unauthorized function replacement.

Technologies: [Spring Cloud Function](https://junglewise.ai/threats/technologies/cloud-function). Vendors: [Spring](https://junglewise.ai/threats/vendors/spring).

## Quick answers

**Is CVE-2026-59299 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-59299 being exploited in the wild.

**How severe is CVE-2026-59299?** Low severity, with a CVSS score of 3.1, published 27 August 2026.

**Which products and versions are affected?** Spring Cloud Function 3.2.16 and earlier, 4.2.0–4.2.7, 4.3.0–4.3.4, 5.0.0–5.0.3.

**Is there a fix for CVE-2026-59299?** 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-2026-59299 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-59299?** Check whether you run Spring Cloud Function 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 exists in the composition lookup mechanism of Spring Cloud Function, which allows functions to be chained together. An attacker can craft requests that poison the base function during composition resolution, causing the framework to use an unintended function. The attack is reachable over the network and does not require authentication. This could lead to arbitrary function invocation or redirection of function calls to attacker-controlled handlers. Patches are available for affected versions.

## Affected products

- Spring Cloud Function 3.2.16 and earlier, 4.2.0–4.2.7, 4.3.0–4.3.4, 5.0.0–5.0.3

## Timeline

- 2026-08-27: disclosed

## References

- [https://spring.io/security/cve-2026-59299](https://spring.io/security/cve-2026-59299)

## Related threats

- [Spring Cloud Function improper HTTP header filtering](https://junglewise.ai/threats/cve-2026-59298-spring-cloud-function-improper-http-header-filtering)
- [Spring Cloud Function isSecure() implementation does not verify HTTPS scheme](https://junglewise.ai/threats/cve-2026-59297-spring-cloud-function-issecure-implementation-does-not-verify)