CVE-2024-24564 is a low-severity (CVSS 3.7) Out-of-bounds Read vulnerability in vyper. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for vyper — see the affected versions and patch details below.
Vyper extract32 can ready dirty memory
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-24564.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
vyperReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
When using the built-in extract32(b, start), if the start index provided has for side effect to update b, the byte array to extract 32 bytes from, it could be that some dirty memory is read and returned by extract32.
As of v0.4.0 (specifically, commit https://github.com/vyperlang/vyper/commit/3d9c537142fb99b2672f21e2057f5f202cde194f), the compiler will panic instead of generating bytecode.
Details
Before evaluating start, the function Extract32.build_IR caches only:
- The pointer in memory/storage to
b: https://github.com/vyperlang/vyper/blob/10564dcc37756f3d3684b7a91fd8f4325a38c4d8/vyper/builtins/functions.py#L916-L918 - The length of
b: https://github.com/vyperlang/vyper/blob/10564dcc37756f3d3684b7a91fd8f4325a38c4d8/vyper/builtins/functions.py#L920-L922
but do not cache the actual content of b. This means that if the evaluation of start changes b's content and length, an outdated length will be used with the new content when extracting 32 bytes from b.
PoC
Calling the function foo of the following contract returns b'uuuuuuuuuuuuuuuuuuuuuuuuuuu\x00\x00789' meaning that extract32 accessed some dirty memory.
var:Bytes[96]
@internal
def bar() -> uint256:
self.var = b'uuuuuuuuuuuuuuuuuuuuuuuuuuuuuu'
self.var = b''
return 3
@external
def foo() -> bytes32:
self.var = b'abcdefghijklmnopqrstuvwxyz123456789'
return extract32(self.var, self.bar(), output_type=bytes32)
# returns b'uuuuuuuuuuuuuuuuuuuuuuuuuuu\x00\x00789'
Impact
For contracts that are affected, it means that calling extract32 returns dirty memory bytes instead of some expected output.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | vyper | all versions | 0.4.0pip install --upgrade 'vyper==0.4.0' |
Affected Products
vypervyperlangResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vyper, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update vyper to 0.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-24564 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.
Frequently Asked Questions
Is CVE-2024-24564 in your dependencies?
Find it across PyPI, including transitive dependencies.