# CVE-2024-24563: Vyper array negative index vulnerability > Vyper compiler allows signed integers as array indices, potentially causing unpredictable behavior or denial of service in smart contracts. - **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 7 Feb 2024 - **Updated:** 17 Jun 2025 - **Also known as:** GHSA-52xq-j7v9-v4v2, PYSEC-2024-150 ## What is CVE-2024-24563? CVE-2024-24563 is a critical vulnerability in vyperlang vyper, published on 7 Feb 2024. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description Vyper is a Pythonic Smart Contract Language for the Ethereum Virtual Machine. Arrays can be keyed by a signed integer, while they are defined for unsigned integers only. The typechecker doesn't throw when spotting the usage of an `int` as an index for an array. The typechecker allows the usage of signed integers to be used as indexes to arrays. The vulnerability is present in different forms in all versions, including `0.3.10`. For ints, the 2's complement representation is used. Because the array was declared very large, the bounds checking will pass Negative values will simply be represented as very large numbers. As of time of publication, a fixed version does not exist. There are three potential vulnerability classes: unpredictable behavior, accessing inaccessible elements and denial of service. Class 1: If it is possible to index an array with a negative integer without reverting, this is most likely not anticipated by the developer and such accesses can cause unpredictable behavior for the contract. Class 2: If a contract has an invariant in the form `assert index < x`, the developer will suppose that no elements on indexes `y | y >= x` are accessible. However, by using negative indexes, this can be bypassed. Class 3: If the index is dependent on the state of the contract, this poses a risk of denial of service. If the state of the contract can be manipulated in such way that the index will be forced to be negative, the array access can always revert (because most likely the array won't be declared extremely large). However, all these the scenarios are highly unlikely. Most likely behavior is a revert on the bounds check. Weakness: CWE-129 (Improper Validation of Array Index) ## Which versions are affected by CVE-2024-24563? 3 open source packages ship an affected version, including vyper. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `vyper` | PyPI | All versions | 0.4.0 | | `vyper` | PyPI | All versions | 0.4.0 | | `vyper` | PyPI | All versions | 0.4.0b1 | Products: Vyperlang Vyper. ## How do I fix CVE-2024-24563? Upgrade vyper to a fixed version for your release line: 0.4.0 or 0.4.0b1. ## Is CVE-2024-24563 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-24563 exists. ## Other vulnerabilities in vyperlang vyper - [CVE-2024-24561](https://insights.sbomify.com/CVE-2024-24561/): Vyper bounds check on built-in `slice()` function can be overflowed (critical 9.8) - [CVE-2023-39363](https://insights.sbomify.com/CVE-2023-39363/): Vyper incorrectly allocated named re-entrancy locks (critical 9.1) - [CVE-2022-24845](https://insights.sbomify.com/CVE-2022-24845/): Integer bounds error in Vyper (high 8.8) - [CVE-2022-29255](https://insights.sbomify.com/CVE-2022-29255/): Multiple evaluation of contract address in call in vyper (high 8.2) - [CVE-2023-42443](https://insights.sbomify.com/CVE-2023-42443/): Vyper vulnerable to memory corruption in certain builtins utilizing `msize` (high 8.1) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2024-24563 and fix it if it is affected. What it is: CVE-2024-24563 is a critical vulnerability in vyperlang vyper, published on 7 Feb 2024. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-24563 exists. Affected packages and fixed versions: - vyper (PyPI): affected all versions; fixed in 0.4.0 - vyper (PyPI): affected all versions; fixed in 0.4.0 - vyper (PyPI): affected all versions; fixed in 0.4.0b1 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2024-24563/ (Markdown: https://insights.sbomify.com/CVE-2024-24563/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2024-24563 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-24563 - OSV: https://osv.dev/vulnerability/CVE-2024-24563 --- From sbomify Insights: https://insights.sbomify.com/CVE-2024-24563/ Summaries are generated and may contain mistakes; the official description above is the record.