vulnerability / NVI-00018466 / Revision 1
flat-to-nested: Prototype pollution in flat-to-nested convert() via __proto__ parent/id key
GitHub lists this reviewed advisory for flat-to-nested. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
7.5 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
flat-to-nested
source listed<= 1.1.1
### Summary `convert()` builds the nested tree by using each flat record's `id` and `parent` field values directly as object keys, with no guard against `__proto__` / `constructor` / `prototype`. A record whose `parent` is the string `"__proto__"` makes `temp[parent]` resolve to `Object.prototype`, and the following `initPush(...)` writes attacker-controlled data onto the global prototype. Any application that passes attacker-influenced records to `convert()` is affected, and the base prototype methods stay intact so the pollution is stealthy. ### Details In `index.js`, `convert()` (`FlatToNested.prototype.convert`): - `temp = {}` (line 45) and `pendingChildOf = {}` (line 46) are plain objects, so they inherit from `Object.prototype`. - For each record, `parent = flatEl[this.config.parent]` (line 51) is taken verbatim from input. - Line 57: `if (temp[parent] !== undefined)` — when `parent === "__proto__"`, `temp["__proto__"]` resolves via the prototype chain to `Object.prototype`, which is `!== undefined`, so the branch is taken. - Line 59: `initPush(this.config.children, temp[parent], flatEl)` → effectively `initPush("children", Object.prototype, flatEl)`. - `i
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-hp36-v28f-w3r4 ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
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