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GHSA-6845-xw22-ffxv

GitHub Security Advisory

Vyper sha3 codegen bug

✓ GitHub Reviewed LOW Has CVE

Advisory Details

### 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.

Affected Packages

PyPI vyper
Affected versions: 0 (fixed in 0.4.0)

Related CVEs

Key Information

GHSA ID
GHSA-6845-xw22-ffxv
Published
February 5, 2024 7:21 PM
Last Modified
November 22, 2024 8:45 PM
CVSS Score
2.5 /10
Primary Ecosystem
PyPI
Primary Package
vyper
GitHub Reviewed
✓ Yes

Dataset

Last updated: September 14, 2025 6:31 AM

Data from GitHub Advisory Database. This information is provided for research and educational purposes.