CVE-2023-40015: Vyper: reversed order of side effects for some operations
First published: Mon Sep 04 2023(Updated: )
### Impact For the following (probably non-exhaustive) list of expressions, the compiler evaluates the arguments from right to left instead of left to right. ``` - unsafe_add - unsafe_sub - unsafe_mul - unsafe_div - pow_mod256 - |, &, ^ (bitwise operators) - bitwise_or (deprecated) - bitwise_and (deprecated) - bitwise_xor (deprecated) - raw_call - <, >, <=, >=, ==, != - in, not in (when lhs and rhs are enums) ``` This behaviour becomes a problem when the evaluation of one of the arguments produces side effects that other arguments depend on. The following expressions can produce side-effect: - state modifying external call - state modifying internal call - `raw_call` - `pop()` when used on a Dynamic Array stored in the storage - `create_minimal_proxy_to` - `create_copy_of` - `create_from_blueprint` For example: ```Vyper f:uint256 @internal def side_effect() -> uint256: self.f = 12 return 1 @external def foo() -> uint256: return unsafe_add(self.f,self.side_effect()) # returns 13 instead of 1 ``` ```Vyper a:DynArray[uint256, 12] @external def bar() -> bool: self.a = [1,2,3] return len(self.a) == self.a.pop() # return false instead of true ``` ### Patches not yet patched, will address in a future release. tracking in https://github.com/vyperlang/vyper/issues/3604. ### Workarounds When using expressions from the list above, make sure that the arguments of the expression do not produce side effects or, if one does, that no other argument is dependent on those side effects. ### References _Are there any links users can visit to find out more?_
Credit: security-advisories@github.com security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Vyperlang Vyper | <=0.3.9 | |
| pip/vyper | <=0.4.0 |
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Reference Links
- https://github.com/vyperlang/vyper/security/advisories/GHSA-g2xh-c426-v8mf
- https://nvd.nist.gov/vuln/detail/CVE-2023-40015
- https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2023-167.yaml
- https://github.com/vyperlang/vyper/issues/3604
- https://github.com/advisories/GHSA-g2xh-c426-v8mf (Advisory)
- https://github.com/vyperlang/vyper/issues/4019
- https://github.com/vyperlang/vyper/pull/4157
Frequently Asked Questions
What is CVE-2023-40015?
CVE-2023-40015 is a vulnerability in the Vyper programming language that affects versions up to and including 0.3.9.
What is the impact of CVE-2023-40015?
CVE-2023-40015 allows an attacker to evaluate arguments in a different order than intended, potentially leading to unexpected behavior or security issues.
What software versions are affected by CVE-2023-40015?
Versions up to and including 0.3.9 of Vyper programming language are affected by CVE-2023-40015.
What is the severity of CVE-2023-40015?
CVE-2023-40015 has a severity value of 5.3, which is considered medium.
How can CVE-2023-40015 be fixed?
To fix CVE-2023-40015, it is recommended to update to a version of Vyper programming language that is not affected by the vulnerability.
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