# CVE-2020-15366: Prototype Pollution in Ajv

> Attackers can execute arbitrary code via prototype pollution in Ajv by providing a crafted JSON schema, affecting applications using this library.

- **Severity:** Medium 5.6 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Jul 2020
- **Updated:** 4 Aug 2024
- **Also known as:** CLSA-2026-1784596282, CLSA-2026-1784683069, CLSA-2026-1789034358, CLSA-2026-1792163462, DEBIAN-CVE-2020-15366, GHSA-v88g-cgmw-v5xw, ROOT-APP-NPM-CVE-2020-15366, UBUNTU-CVE-2020-15366

## What is CVE-2020-15366?

CVE-2020-15366 is a medium-severity code injection vulnerability in n/a, published on 15 Jul 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in ajv.validate() in Ajv (aka Another JSON Schema Validator) 6.12.2. A carefully crafted JSON schema could be provided that allows execution of other code by prototype pollution. (While untrusted schemas are recommended against, the worst case of an untrusted schema should be a denial of service, not execution of code.)

Weakness: CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes)

## Which versions are affected by CVE-2020-15366?

2 open source packages ship an affected version, including ajv. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ajv` | npm | All versions | 6.12.3 |
| `ajv` | npm | All versions | 6.12.3 |

Products: Ajv.js Ajv.

## How do I fix CVE-2020-15366?

Upgrade ajv to 6.12.3 or later.

## Is CVE-2020-15366 being exploited?

There is no known exploitation of CVE-2020-15366 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-15366 and fix it if it is affected.

What it is: CVE-2020-15366 is a medium-severity code injection vulnerability in n/a, published on 15 Jul 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-15366 in the wild and no public exploit code.

Affected packages and fixed versions:
- ajv (npm): affected all versions; fixed in 6.12.3
- ajv (npm): affected all versions; fixed in 6.12.3

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/CVE-2020-15366/ (Markdown: https://insights.sbomify.com/CVE-2020-15366/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-15366
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-15366
- OSV: https://osv.dev/vulnerability/CVE-2020-15366

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-15366/
Summaries are generated and may contain mistakes; the official description above is the record.