🛡️ Sentinel: [CRITICAL] Fix Prototype Pollution vulnerability in label dictionary#33
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…l dictionary
- Replaced plain object literal with `Object.create ? Object.create(null) : {}` for labels dictionary initialization.
- Added Sentinel journal entry in `.jules/sentinel.md` noting the vulnerability and prevention.
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Pull request overview
This PR addresses a security issue in luaparse.js by preventing prototype-related key collisions/mutation in the internal labels dictionary used for Lua 5.2+ goto / label flow tracking, and records the incident in a Sentinel learning log.
Changes:
- Initialize
FullFlowContext’sscope.labelswith a null-prototype dictionary (Object.create(null)) instead of{}. - Add
.jules/sentinel.mddocumenting the prototype-pollution class of issue and the preferred prevention strategy.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.
| File | Description |
|---|---|
luaparse.js |
Switches labels from a plain object to a prototype-less dictionary to avoid __proto__-style key hazards. |
.jules/sentinel.md |
Adds a Sentinel entry describing the vulnerability and the intended prevention approach. |
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| var scope = { | ||
| labels: {}, | ||
| labels: Object.create ? Object.create(null) : {}, | ||
| locals: [], |
| var scope = { | ||
| labels: {}, | ||
| labels: Object.create ? Object.create(null) : {}, | ||
| locals: [], |
| ## 2024-05-27 - [Prototype Pollution in Lua labels dictionary] | ||
| **Vulnerability:** A prototype pollution vulnerability existed in `luaparse.js` where the `labels` dictionary for the flow context scope was initialized using a standard object literal `{}`. This allows a malicious Lua script with labels named after Object prototype properties (e.g., `::__proto__::`) to pollute the Javascript prototype and cause Denial of Service or logic bypasses in the lexer and surrounding ecosystem. | ||
| **Learning:** In Javascript parsers analyzing user-provided identifiers and labels, using plain object literals as dictionaries is unsafe as properties like `__proto__` can be accessed or overwritten. | ||
| **Prevention:** Always initialize dictionaries storing user-controlled keys using `Object.create(null)` to create a prototype-less object, ensuring secure property assignments and lookups. Due to the environment potentially missing polyfills, a secure fallback `Object.create ? Object.create(null) : {}` should be used. |
| **Vulnerability:** A prototype pollution vulnerability existed in `luaparse.js` where the `labels` dictionary for the flow context scope was initialized using a standard object literal `{}`. This allows a malicious Lua script with labels named after Object prototype properties (e.g., `::__proto__::`) to pollute the Javascript prototype and cause Denial of Service or logic bypasses in the lexer and surrounding ecosystem. | ||
| **Learning:** In Javascript parsers analyzing user-provided identifiers and labels, using plain object literals as dictionaries is unsafe as properties like `__proto__` can be accessed or overwritten. |
🚨 Severity: CRITICAL
đź’ˇ Vulnerability: A prototype pollution vulnerability existed in
luaparse.jswhere thelabelsdictionary for the flow context scope was initialized using a standard object literal{}. This allows a malicious Lua script with labels named after Object prototype properties (e.g.,::__proto__::) to pollute the Javascript prototype and cause unexpected behaviour or logic bypasses in the lexer and surrounding ecosystem.🎯 Impact: Denial of Service (DoS) and potential logic corruption depending on how the parsed AST is consumed by applications, as arbitrary properties on
Object.prototypecould be overridden or instantiated.🔧 Fix: Initialized the labels dictionary using
Object.create ? Object.create(null) : {}to safely construct a dictionary without inheriting fromObject.prototype. Added a learning to.jules/sentinel.md.âś… Verification: Create a script initializing the parser and passing a Lua source like
::__proto__::. It should not crash or throw exceptions internally. Runnpm run testto verify parser functionality remains unaltered.PR created automatically by Jules for task 16078060755960758820 started by @ericbfriday