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Fix OOB panic in FlexBuffers Rust get_bool/read_usize and UAF in C++ SymbolTable::Add #9105

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Fix OOB panic in FlexBuffers Rust get_bool/read_usize and UAF in C++ SymbolTable::Add #9105

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7ab2d0e
flexbuffers Rust: fix OOB panic in get_bool() and read_usize() on cra…
XananasX7 May 26, 2026
6b866e3
Fix use-after-free in SymbolTable::Add() via reordering emplace_back …
XananasX7 May 26, 2026
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4 changes: 3 additions & 1 deletion include/flatbuffers/idl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -245,9 +245,11 @@ class SymbolTable {
}

bool Add(const std::string& name, T* e) {
vec.emplace_back(e);
// Check for duplicate before adding to vec to avoid use-after-free:
// if caller deletes `e` on duplicate, the pointer must not remain in vec.
auto it = dict.find(name);
if (it != dict.end()) return true;
vec.emplace_back(e);
dict[name] = e;
return false;
}
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11 changes: 8 additions & 3 deletions rust/flexbuffers/src/reader/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -323,7 +323,12 @@ impl<B: Buffer> Reader<B> {
/// Otherwise Returns error.
pub fn get_bool(&self) -> Result<bool, Error> {
self.expect_type(FlexBufferType::Bool)?;
Ok(self.buffer[self.address..self.address + self.width.n_bytes()].iter().any(|&b| b != 0))
Ok(self
.buffer
.get(self.address..self.address + self.width.n_bytes())
.ok_or(Error::FlexbufferOutOfBounds)?
.iter()
.any(|&b| b != 0))
}

/// Gets the length of the key if this type is a key.
Expand Down Expand Up @@ -601,9 +606,9 @@ fn f64_from_le_bytes(bytes: [u8; 8]) -> f64 {
}

fn read_usize(buffer: &[u8], address: usize, width: BitWidth) -> usize {
let cursor = &buffer[address..];
let cursor = buffer.get(address..).unwrap_or_default();
match width {
BitWidth::W8 => cursor[0] as usize,
BitWidth::W8 => cursor.first().copied().unwrap_or_default() as usize,
BitWidth::W16 => cursor
.get(0..2)
.and_then(|s| s.try_into().ok())
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