Mooncake transfer engine: Unauthenticated memory read and write via TCP transport
Summary
The Mooncake transfer engine before 0.3.13 trusts an address supplied over the network in its TCP transport data port. An unauthenticated attacker who can reach that port can read and write arbitrary memory of the engine process. This can expose KV cache contents, prompts and secrets, and write access could lead to code execution.
Affected
- Mooncake transfer engine (kvcache-ai) before 0.3.13 (CNA record: affected 0 to < 0.3.13)
- Python package mooncake-transfer-engine (reporter: <= 0.3.12.post1)
Fixed in
- Fix commit a2933849417259e562fc9cbad63c618d464dfb2d adds address validation against registered buffers
- Recommended target: 0.3.13.post1 or later
- First fixed version: not confirmed, sources conflict (0.3.12, 0.3.12.post1 or 0.3.13)
Workaround
- Restrict the TCP transport data port to trusted internal nodes only
- A WAF offers only limited protection unless it validates the Mooncake SessionHeader structure
Exploitation
- CISA SSVC: exploitation status poc, automatable yes, technical impact total
- Public technical details of the mechanism exist in issue #4441, which reports runtime confirmation on 0.3.11.post1
- No confirmed in-the-wild exploitation; not listed in CISA KEV
Our recommendation
- Identify all Mooncake installations, including Python dependencies in AI tooling
- Upgrade to 0.3.13.post1 or later and check the release notes first
- If patching is not possible, block the data port from untrusted networks
- Check that the HTTP metadata server is also restricted, as CVE-2026-103765 affects it
- Monitor for unusual connections to the data port
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Fix commit a2933849417259e562fc9cbad63c618d464dfb2d github.com
- Mooncake issue #4441 (technical details) github.com
- Mooncake release v0.3.13 github.com
- VulnCheck advisory www.vulncheck.com
- OSV record CVE-2026-103764 osv.dev
- VulDB CVE-2026-103764 vuldb.com
- OpenCVE CVE-2026-103764 app.opencve.io
- TheHackerWire CVE-2026-103764 www.thehackerwire.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 31 Oct 2026, 03:37.
Original description (NVD)
Mooncake transfer engine before 0.3.13 contains an untrusted pointer dereference in ServerSession::readHeader that allows unauthenticated attackers to read and write arbitrary process memory via the TCP transport data port. Attackers can send a crafted SessionHeader with arbitrary addr and size values using READ or WRITE opcodes to disclose KV cache contents, prompts and secrets or corrupt memory toward code execution.
NVD references (7)
- https://github.com/kvcache-ai/Mooncake
- https://github.com/kvcache-ai/Mooncake/blob/6041a609a8c3af35e778f70db344f145c2914980/mooncake-transfer-engine…
- https://github.com/kvcache-ai/Mooncake/commit/a2933849417259e562fc9cbad63c618d464dfb2d
- https://github.com/kvcache-ai/Mooncake/issues/4441
- https://github.com/kvcache-ai/Mooncake/releases/tag/v0.3.13
- https://www.vulncheck.com/advisories/mooncake-transfer-engine-before-0.3.13-unauthenticated-arbitrary-memory-…
- https://github.com/kvcache-ai/Mooncake/issues/4441
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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