Summary
CVE-2026-115812 is a relative path traversal vulnerability (CWE-23) in the model archive extraction of Amazon Web Services Multi Model Server (MMS) 1.1.11 and earlier. A crafted model archive might allow remote actors to execute arbitrary code. The CVSS v3.1 base score is 9.8 (Critical). MMS is end-of-life and no fixed version exists.
Technical details
- Root cause: Relative path traversal during model archive extraction. Archive entries can be written outside the intended target directory.
- Trigger conditions: MMS loads a crafted model archive. AWS notes that the MMS management interface does not require authentication, which compounds the issue.
- Attack vector: Network. No privileges or user interaction are required.
- Impact: Arbitrary file write beyond the extraction directory, which might lead to arbitrary code execution.
- Related issue: The same AWS bulletin covers CVE-2026-115813, where the management interface could be misdirected to unintended network destinations. This is a separate CVE.
Affected software
- AWS Multi Model Server: all released versions up to and including 1.1.11.
- MMS reached end of life on November 20, 2025. Its repository is archived and read-only.
Severity
- CVSS v3.1 base score: 9.8 (Critical)
- Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Mitigation and recommended actions
- Immediate: No patched version is available. AWS recommends discontinuing MMS and migrating to an actively supported model-serving alternative.
- Derivative code: If you maintain derivative code, validate paths so that archive entries outside the extraction directory are rejected. Restrict model downloads to an approved URL allowlist.
- If migration is not immediately feasible:
- Bind the management interface to the loopback address only.
- Do not accept externally supplied URLs for model downloads.
- SageMaker deployments cannot apply the loopback workaround without disabling model loading. Prioritize migration for these deployments and restrict access to the serving port to trusted systems only.

