# CVE-2026-96763: kvcache-ai Mooncake access control bypass in MountSegment

Source: https://junglewise.ai/threats/cve-2026-96763-a-security-flaw-has-been-discovered-in-kvcache-ai-mooncake-up-to  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-24. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-96763 · Severity: medium · CVSS 5.4 · Published 2026-09-24

Mooncake, a distributed storage system, fails to validate that a client owns the resources it claims during segment registration. An attacker can register a fake storage segment that points to another client's memory and Transfer Engine endpoint, then write arbitrary data to that victim's memory during normal storage operations. This allows cross-client data corruption and integrity violations without requiring access to the victim's systems.

Technologies: [Kvcache-Ai Mooncake](https://junglewise.ai/threats/technologies/mooncake). Vendors: [Kvcache-Ai](https://junglewise.ai/threats/vendors/kvcache-ai).

## Quick answers

**Is CVE-2026-96763 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-96763 being exploited in the wild.

**How severe is CVE-2026-96763?** Medium severity, with a CVSS score of 5.4, published 24 September 2026.

**Which products and versions are affected?** Kvcache-Ai Mooncake up to 0.3.12, 0.3.13.post1, 0.3.14-rc1.

**Is there a fix for CVE-2026-96763?** 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-2026-96763 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-96763?** Check whether you run Kvcache-Ai Mooncake 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 in ScopedSegmentAccess::MountSegment (segment.cpp) which does not verify that the Transfer Engine endpoint and memory address range supplied by a client actually belong to that client. An attacker can submit a MountSegment request with a victim's real endpoint and registered memory range, create an allocator from these forged credentials, and then use preferred-segment allocation to write attacker-controlled data to the victim's memory via the Transfer Engine data plane. The attack requires network access to the Mooncake Store Master but no authentication or victim interaction.

## Affected products

- kvcache-ai Mooncake up to 0.3.12, 0.3.13.post1, 0.3.14-rc1

## Timeline

- 2026-09-24: disclosed: CVE-2026-96763 published
- 2026-07-24: other: Proof of concept released on GitHub

## References

- [https://gist.github.com/yyymk/fea24846dc31042cb472d7bd496a8438](https://gist.github.com/yyymk/fea24846dc31042cb472d7bd496a8438)
- [https://vuldb.com/cve/CVE-2026-96763](https://vuldb.com/cve/CVE-2026-96763)

## Related threats

- [Mooncake missing authentication in HTTP metadata server](https://junglewise.ai/threats/cve-2026-103765-mooncake-through-0-3-13-post1-contains-a-missing-authentication)
- [kvcache-ai mooncake denial of service in regex metadata queries](https://junglewise.ai/threats/cve-2026-96764-a-weakness-has-been-identified-in-kvcache-ai-mooncake-up-to-0-3)
- [Kvcache-ai Mooncake authorization bypass in RPC segment handler](https://junglewise.ai/threats/cve-2026-96762-a-vulnerability-was-determined-in-kvcache-ai-mooncake-up-to-0-3)