CVE-2024-26149 is a low-severity (CVSS 3.7) Buffer Overflow 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 _abi_decode Memory Overflow
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-2024-26149.
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
If an excessively large value is specified as the starting index for an array in _abi_decode, it can cause the read position to overflow. This results in the decoding of values outside the intended array bounds, potentially leading to bugs in contracts that use arrays within _abi_decode. The advisory has been assigned low severity, because it is only observable if there is a memory write between two invocations of abi_decode on the same input.
Proof of Concept
event Pwn:
pass
@external
def f(x: Bytes[32 * 3]):
a: Bytes[32] = b"foo"
y: Bytes[32 * 3] = x
decoded_y1: Bytes[32] = _abi_decode(y, Bytes[32])
a = b"bar"
decoded_y2: Bytes[32] = _abi_decode(y, Bytes[32])
if decoded_y1 != decoded_y2:
log Pwn()
Sending the following calldata results in Pwn being emitted.
0xd45754f8
0000000000000000000000000000000000000000000000000000000000000020
0000000000000000000000000000000000000000000000000000000000000060
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffa0
Patches
Patched in https://github.com/vyperlang/vyper/pull/3925, https://github.com/vyperlang/vyper/pull/4091, https://github.com/vyperlang/vyper/pull/4144, https://github.com/vyperlang/vyper/pull/4060.
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-2024-26149 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-2024-26149 in your dependencies?
Find it across PyPI, including transitive dependencies.