CVE-2024-24559: Vyper SHA3 code generation bug
First published: Mon Feb 05 2024(Updated: )
### Summary There is an error in the stack management when compiling the `IR` for `sha3_64`. Concretely, the `height` variable is miscalculated. The vulnerability can't be triggered without writing the `IR` by hand. That is, it cannot be triggered from regular vyper code, it can only be triggered by using the `fang` binary directly (this binary used to be called `vyper-ir` prior to v0.3.4). ### Details To compile `sha3_64`, the `arg[0]` and `arg[1]` have to be compiled: https://github.com/vyperlang/vyper/blob/c150fc49ee9375a930d177044559b83cb95f7963/vyper/ir/compile_ir.py#L585-L586 As can be seen, after compiling the 0th arg, the `height` variable isn't increased. If new `withargs` are defined in the inner scope, they are manipulated correctly, because both their `height` is off and also the global `height` is off and thus their placement on the stack is computed correctly. `sha3_64` is used for retrieval in mappings. No flow that would cache the `key` was found, the issue shouldn't be possible to trigger when compiling the compiler-generated `IR`. ### PoC Suppose the following hand-written IR: ```lisp (with _loc (with val 1 (with key 2 (sha3_64 val key))) (seq (sstore _loc (with x (sload _loc) (with ans (add x 1) (seq (assert (ge ans x)) ans)))))) ``` after compilation: ``` the generated bytecode: 6001600281806020525f5260405f2090509050805460018101818110610026579050815550005b5f80fd 0000 60 PUSH1 0x01 0002 60 PUSH1 0x02 0004 81 DUP2 0005 80 DUP1 *********** bad code here!!!!!! 0006 60 PUSH1 0x20 0008 52 MSTORE ``` It can be seen that the second `DUP` will dup the item on the top of the stack which is incorrect. ### Patches Patched in https://github.com/vyperlang/vyper/pull/4063. ### Impact Versions v0.2.0-v0.3.10 were evaluated, and access of the variable with the invalid height is not reachable from IR generated by the vyper front-end. Because the issue isn't triggered during normal compilation of vyper code, the impact is considered low.
Credit: security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Vyperlang Vyper | <=0.3.10 | |
| pip/vyper | <0.4.0 | 0.4.0 |
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Reference Links
- https://github.com/vyperlang/vyper/blob/c150fc49ee9375a930d177044559b83cb95f7963/vyper/ir/compile_ir.py#L585-L586
- https://github.com/vyperlang/vyper/security/advisories/GHSA-6845-xw22-ffxv
- https://nvd.nist.gov/vuln/detail/CVE-2024-24559
- https://github.com/vyperlang/vyper/pull/4063
- https://github.com/vyperlang/vyper/commit/d9f9fdadd81a148cbc68f02dbbbcdc0c92fad652
- https://github.com/advisories/GHSA-6845-xw22-ffxv (Advisory)
- https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2024-147.yaml
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