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cleverbrush deep CVE-2026-78654

| EUVDEUVD-2026-65304 MEDIUM
Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution) (CWE-1321)
2026-08-25 VulDB GHSA-85f3-5c6p-wf9v
Information Disclosure Prototype Pollution Framework Deep
5.5
CVSS 4.0 · Vendor: VulDB
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Severity by source

Vendor (VulDB) PRIMARY
5.5 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
8.3 HIGH

Network-reachable with no auth required; S:C assigned because successful exploitation mutates Object.prototype, extending impact beyond the vulnerable component to the entire JavaScript runtime.

3.1 AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:L/SI:L/SA:N

Primary rating from Vendor (VulDB).

CVSS VectorVendor: VulDB

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

4
Source Code Evidence Fetched
Aug 25, 2026 - 07:42 vuln.today
Analysis Generated
Aug 25, 2026 - 07:42 vuln.today
CVSS changed
Aug 25, 2026 - 06:22 NVD
6.9 (MEDIUM) 5.5 (MEDIUM)
CVE Published
Aug 25, 2026 - 06:00 cve.org
MEDIUM 5.5

DescriptionCVE.org

A vulnerability has been found in cleverbrush framework and deep up to 4.4.0. This impacts the function deepExtend of the file libs/deep/src/deepExtend.ts. The manipulation leads to improperly controlled modification of object prototype attributes. Remote exploitation of the attack is possible. The exploit has been disclosed to the public and may be used. Upgrading to version 4.4.1 will fix this issue. The identifier of the patch is 810398c1308c500c3b8b6af380b5a89371389327. You should upgrade the affected component.

AnalysisAI

Prototype pollution in the @cleverbrush/deep package (versions ≤ 4.4.0) allows a remote attacker to corrupt Object.prototype by supplying crafted JSON containing reserved JavaScript keys (__proto__, constructor, prototype) to the deepExtend() function without any privilege requirement. Any Node.js application that passes externally controlled input through deepExtend() is at risk of property injection affecting every plain object in the runtime, potentially enabling authentication bypass or logic manipulation downstream. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Send crafted JSON with __proto__ key to application endpoint
Delivery
Application parses JSON and passes payload to deepExtend()
Exploit
deepExtend() merges __proto__ without key filtering
Execution
Object.prototype mutated with attacker-controlled properties
Persist
All subsequent plain objects inherit injected properties
Impact
Bypass security checks or corrupt application logic
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Vulnerability AssessmentAI

Exploitation Exploitation requires that the target application uses `@cleverbrush/deep` (or `@cleverbrush/framework`) at version 4.4.0 or earlier AND passes attacker-controlled data - such as a parsed JSON request body, query parameter, or file upload - into `deepExtend()` without prior sanitization of prototype-polluting keys. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The provided CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N with VC:L/VI:L/VA:L and SC:N/SI:N/SA:N, E:P) yields a score of 5.5, reflecting low-complexity network exploitation with limited per-system impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker sends a crafted HTTP POST request with the JSON body `{"__proto__":{"isAdmin":true}}` to any endpoint that parses the body and passes it to `deepExtend()` on versions ≤ 4.4.0. The function merges the payload recursively without filtering the `__proto__` key, silently modifying `Object.prototype` so that every subsequent plain object literal in the process inherits `isAdmin: true`. …
Remediation Upgrade `@cleverbrush/deep` to version 4.4.1, which resolves the issue by filtering `__proto__`, `constructor`, and `prototype` keys at every recursion depth within `deepExtend()`. … Detailed patch versions, workarounds, and compensating controls in full report.
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Same weakness CWE-1321 – Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution)

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Same technique Information Disclosure

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CVE-2015-1701 HIGH POC
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CVE-2014-6324 HIGH POC
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CVE-2026-78654 vulnerability details – vuln.today
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