EUVD-2026-37943
GHSA-9v98-6g37-x9g6
Severity by source
AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L
Network-reachable client protocol (AV:N), trivial crafted path (AC:L), needs an authenticated writer (PR:L), no UI; prototype pollution leaves the record subsystem and taints the permission valve, so S:C with high C/I and low A.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L
Lifecycle Timeline
3DescriptionCVE.org
deepstream is a server that allows clients and backend services to sync data, send messages and make rpcs at scale. Versions prior to 10.0.5 are vulnerable to Prototype Pollution. Exploitation can lead to potential privilege escalation from any authenticated user with write permission to any record. This issue has been fixed in version 10.0.5.
AnalysisAI
Prototype pollution in deepstream.io versions prior to 10.0.5 allows an authenticated client with write permission to any record to corrupt the Node.js Object prototype by submitting record-update messages whose path contains tokens such as __proto__, constructor, or prototype. Because deepstream's permission valve and record-transition pipeline both invoke setValue with the attacker-controlled path, polluting the prototype can taint subsequent permission and transition logic and lead to privilege escalation across all connected clients. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires an authenticated deepstream.io client session (PR:L in the vendor vector) that holds write permission to at least one record under the server's Valve permission rules, network reachability to the deepstream server's client port, and a server running a version prior to 10.0.5 with the default json-path utility - no user interaction, no admin role, and no non-default feature flag is needed. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | Vendor CVSS 3.1 of 9.9 (AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L) reflects a network-reachable, low-complexity attack from any authenticated record-writer, with scope change because polluting Object.prototype reaches code outside the record subsystem (notably the permission valve seen in the diff) - a credible justification for S:C rather than CVSS inflation. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker logs in as a normal deepstream client with write access to even one record (the default for many collaborative-app deployments) and sends a record-update message such as record set with path '__proto__.isAdmin' and value true. The unsafe setValue walks through Object.prototype, so every subsequent object - including data evaluated by the Valve permission engine on later requests - inherits isAdmin=true, allowing the attacker to bypass per-record access controls and escalate privileges across the entire deepstream cluster until the process is restarted. |
| Remediation | Vendor-released patch: deepstream.io 10.0.5 - upgrade the server package to 10.0.5 or later per GHSA-9v98-6g37-x9g6 (https://github.com/deepstreamIO/deepstream.io/security/advisories/GHSA-9v98-6g37-x9g6) and commit 54b8e2958a98df444b5b5d9a66e22872afd84e44, which introduces isValidPath rejecting __proto__/constructor/prototype tokens and wraps the permission-valve setValue in try/catch. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Identify all deepstream.io deployments and their exact version numbers; document which users hold write permissions to deepstream records. …
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External POC / Exploit Code
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