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JS: Stop treating parseInt and parseFloat as whole-string number guards - #23121
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🟡 Changes recommended
The shared guard change can introduce prototype-pollution false positives for numerically guarded keys, requiring a query-specific guard and regression coverage.
2 open issues
What changed in this PR
This PR corrects JavaScript taint analysis so numeric-prefix parsing no longer sanitizes the original string, allowing injection queries to detect trailing payloads.
Changes:
- Removes
parseIntandparseFloathandling fromisNumberGuard, preserving whole-value checks. - Updates
parseIntalert expectations and addsparseFloatregression coverage plus a safe parsed-value case. - Adds a change note describing potentially newly reported alerts.
| File | Description |
|---|---|
javascript/ql/test/query-tests/Security/CWE-078/UnsafeShellCommandConstruction/UnsafeShellCommandConstruction.expected |
Records alerts for unsafe numeric-prefix guards. |
javascript/ql/test/query-tests/Security/CWE-078/UnsafeShellCommandConstruction/lib/lib.js |
Updates guard expectations and adds regression cases. |
javascript/ql/lib/semmle/javascript/dataflow/TaintTracking.qll |
Stops treating prefix parsing as whole-string validation. |
javascript/ql/lib/change-notes/2026-11-12-isnumberguard-parseint.md |
Documents the analysis change and affected alerts. |
Review effort: Max (auto)
| @@ -989,13 +989,6 @@ module TaintTracking { | |||
| | | |||
| operand = isNaN.getArgument(0).asExpr() | |||
| or | |||
Contributor
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This should be investigated before merging.
| @@ -989,13 +989,6 @@ module TaintTracking { | |||
| | | |||
| operand = isNaN.getArgument(0).asExpr() | |||
| or | |||
owen-mc
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Nov 12, 2026
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| exists(DataFlow::CallNode parse | | ||
| parse = DataFlow::globalVarRef(["parseInt", "parseFloat"]).getACall() | ||
| | | ||
| parse = isNaN.getArgument(0) and | ||
| operand = parse.getArgument(0).asExpr() | ||
| ) | ||
| or |
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A corresponding disjunct should be added to the characteristic predicate of NumberGuard for prototype pollution, as the case that is being removed is still valid for the purpose of that class.
owen-mc
approved these changes
Nov 13, 2026
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Fixes #23115
Summary
TaintTracking::isNumberGuardtreatedisNaN(parseInt(x))andisNaN(parseFloat(x))as checks thatxis a number. Both functions read only a leading numeric prefix and ignore trailing characters, so the original stringxcan still carry a payload to a sink. Remove theparseIntandparseFloatbranch fromisNumberGuard. Whole-value checks such asisNaN(x),isNaN(+x),isNaN(x - 0), andtypeof x === "number"remain unchanged.Evidence
codeql test runpasses onUnsafeShellCommandConstructionand the otherisNumberGuardquery suites.