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[Swift] Fix verifier accepting truncated scalar vectors (OOB read/write, RCE) #9081

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Merged
mustiikhalil merged 1 commit into from
May 8, 2026
+29 −1
Merged

[Swift] Fix verifier accepting truncated scalar vectors (OOB read/write, RCE) #9081

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9 changes: 8 additions & 1 deletion swift/Sources/FlatBuffers/Verifiable.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -56,8 +56,15 @@ extension Verifiable {
let len: UOffset = try verifier.getValue(at: position)
let intLen = Int(len)
let start = Int(clamping: (position &+ MemoryLayout<Int32>.size).magnitude)
let byteCount = intLen.multipliedReportingOverflow(
by: MemoryLayout<T>.size)
guard !byteCount.overflow else {
throw FlatbuffersErrors.outOfBounds(
position: UInt.max,
end: verifier.capacity)
}
try verifier.isAligned(position: start, type: type.self)
try verifier.rangeInBuffer(position: start, size: intLen)
try verifier.rangeInBuffer(position: start, size: byteCount.partialValue)
return (start, intLen)
}
}
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21 changes: 21 additions & 0 deletions tests/swift/Tests/Flatbuffers/FlatbuffersVerifierTests.swift
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Expand Up @@ -411,6 +411,27 @@ final class FlatbuffersVerifierTests {
}
}

@Test(.bug("https://github.com/google/flatbuffers/issues/9082"))
func testRejectsTruncatedScalarVector() {
// swiftformat:disable all
var byteBuffer = ByteBuffer(bytes: [
16, 0, 0, 0,
6, 0, 8, 0,
4, 0, 0, 0,
0, 0, 0, 0,
12, 0, 0, 0,
8, 0, 0, 0,
0, 0, 0, 0,
2, 0, 0, 0,
65, 66,
])
// swiftformat:enable all

#expect(throws: FlatbuffersErrors.self) {
try getCheckedRoot(byteBuffer: &byteBuffer) as Swift_Tests_Vectors
}
}

@Test
func testValidUnionBuffer() {
let string = "Awesome \\\\t\t\nstring!"
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