GHSA-4q55-j62x-fr9h devalue: Malformed null-prototype object keys bypass __proto__ rejection via property-key coercion
Not scored
Published
Check this codebase for GHSA-4q55-j62x-fr9h and fix it if it is affected.
What it is: GHSA-4q55-j62x-fr9h is a vulnerability in devalue, published on 1 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of GHSA-4q55-j62x-fr9h in the wild and no public exploit code.
Affected packages and fixed versions:
- devalue (npm): affected all versions; fixed in 5.9.3
- devalue (npm): affected all versions; fixed in 5.9.3
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/GHSA-4q55-j62x-fr9h/ (Markdown: https://insights.sbomify.com/GHSA-4q55-j62x-fr9h/index.md)
Malformed keys in devalue bypass __proto__ rejection, potentially allowing prototype pollution, though impact is deemed unlikely.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is GHSA-4q55-j62x-fr9h?
GHSA-4q55-j62x-fr9h is a vulnerability in devalue, published on 1 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
This is another instance of https://github.com/sveltejs/devalue/security/advisories/GHSA-mwv9-gp5h-frr4, where some payloads could cause
parse to create objects with a __proto__ own property. This on its own is not enough to cause prototype pollution, and indeed this is actually how JSON.parse works, but we decided to be a little more defensive here and not allow the creation of objects with __proto__ own-properties. It is very unlikely for this to cause any issues.Which versions are affected by GHSA-4q55-j62x-fr9h?
2 open source packages ship an affected version, including devalue.
| Package | Affected | Fixed in |
|---|---|---|
devalue npm | All versions | 5.9.3 |
devalue npm | All versions | 5.9.3 |
How do I fix GHSA-4q55-j62x-fr9h?
Upgrade devalue to 5.9.3 or later.
Is GHSA-4q55-j62x-fr9h being exploited?
There is no known exploitation of GHSA-4q55-j62x-fr9h in the wild and no public exploit code.