LMCache: Missing authentication in MP coordinator fleet control API
Summary
LMCache up to and including 0.5.5 contains a missing authentication flaw in its multiprocess (MP) coordinator. The HTTP fleet control API listens on all interfaces by default. A remote, unauthenticated attacker who can reach the port can register or deregister instances, overwrite quotas, inject events and enumerate cache keys. This can disrupt KV caching and disclose placement metadata. No code execution is described.
Affected
- LMCache 0.5.5 and earlier (MP coordinator)
Fixed in
Unknown. No patched version had been released at the time of research. A fix is under review (GitHub PR #6174, merge status unconfirmed).
Workaround
- No official workaround from the vendor.
- Restrict port 9300 (coordinator) and port 9000 (controller API server) to localhost or trusted management networks using host binding, firewall rules or network segmentation.
- The controller API server exposes a similar unauthenticated surface, so restricting only the coordinator is not sufficient.
Exploitation
- Known exploited (KEV): no evidence found.
- The issue reporter confirmed the flaw at runtime on 0.5.5. No separate public exploit repository was found.
- CISA SSVC: exploitation none, automatable yes, technical impact partial.
Our recommendation
- Inventory: check for lmcache in Python environments, container images and Helm charts, and confirm whether version 0.5.5 or earlier is used.
- Restrict ports 9300 and 9000 to trusted networks now.
- Monitor the upstream repository for a released fix, upgrade once available, and verify that the controller API server is covered.
- Treat the cache management plane as internal only.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE-2026-107205 VulnCheck advisory www.vulncheck.com
- LMCache issue #5508 github.com
- LMCache v0.5.5 app.py (MP coordinator) github.com
- LMCache v0.5.5 config.py (MP coordinator) github.com
- LMCache pull request #6174 github.com
- LMCache GitHub repository github.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, 21:21.
Original description (NVD)
LMCache through 0.5.5 contains a missing authentication vulnerability in the multiprocess coordinator that allows remote unauthenticated attackers to access its HTTP fleet control API listening on all interfaces by default. Attackers can register or deregister instances via /instances, overwrite quotas via /quota endpoints, inject events via /events, and enumerate /directory/keys to disrupt caching and disclose placement metadata.
NVD references (5)
- https://github.com/LMCache/LMCache
- https://github.com/LMCache/LMCache/blob/v0.5.5/lmcache/v1/mp_coordinator/app.py#L238-L246
- https://github.com/LMCache/LMCache/blob/v0.5.5/lmcache/v1/mp_coordinator/config.py#L71
- https://github.com/LMCache/LMCache/issues/5508
- https://www.vulncheck.com/advisories/lmcache-through-0.5.5-missing-authentication-in-mp-coordinator-fleet-con…
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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