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GHSA-3p37-3636-q8wv

GitHub Security Advisory

Vyper vulnerable to OOB DynArray access when array is on both LHS and RHS of an assignment

✓ GitHub Reviewed HIGH Has CVE

Advisory Details

### Impact
during codegen, the length word of a dynarray is written before the data, which can result in OOB array access in the case where the dynarray is on both the lhs and rhs of an assignment. here is a minimal example producing the issue:
```vyper
a:DynArray[uint256,3]
@external
def test() -> DynArray[uint256,3]:
self.a = [1,2,3]
self.a = empty(DynArray[uint256,3])
self.a = [self.a[0],self.a[1],self.a[2]]
return self.a # return [1,2,3]
```

and here is an example demonstrating the issue can cause data corruption across call frames:

```vyper
@external
def test() -> DynArray[uint256,3]:
self.a()
return self.b() # return [1,2,3]

@internal
def a():
a: uint256 = 0
b: uint256 = 1
c: uint256 = 2
d: uint256 = 3

@internal
def b() -> DynArray[uint256,3]:
a: DynArray[uint256,3] = empty(DynArray[uint256,3])
a = [a[0],a[1],a[2]]
return a
```

examples involving append and pop:
```vyper
@internal
def foo():
c: DynArray[uint256, 1] = []
c.append(c[0])
```

```vyper
@internal
def foo():
c: DynArray[uint256, 1] = [1]
c[0] = c.pop()
```

the expected behavior in all of the above cases is to revert due to oob array access.

### Patches
patched in 4f8289a81206f767df1900ac48f485d90fc87edb

### Workarounds
_Is there a way for users to fix or remediate the vulnerability without upgrading?_

### References
_Are there any links users can visit to find out more?_

Affected Packages

PyPI vyper
Affected versions: 0 (fixed in 0.3.8)

Related CVEs

Key Information

GHSA ID
GHSA-3p37-3636-q8wv
Published
May 12, 2023 8:21 PM
Last Modified
November 19, 2024 4:32 PM
CVSS Score
7.5 /10
Primary Ecosystem
PyPI
Primary Package
vyper
GitHub Reviewed
✓ Yes

Dataset

Last updated: June 18, 2025 6:25 AM

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