# CVE-2026-44291: protobufjs: Code generation gadget after prototype pollution

> Attackers can execute arbitrary code via prototype pollution in protobufjs by injecting malicious strings into generated JavaScript functions.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:H/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:** 13 May 2026
- **Updated:** 13 May 2026
- **Also known as:** CLEANSTART-2026-JH02542, CLEANSTART-2026-OR18491, CLEANSTART-2026-QG09459, ECHO-3792-9b0f-a42e, GHSA-75px-5xx7-5xc7, MINI-5f8r-wjwf-pvpg, MINI-5gwv-m53w-w2qx, MINI-6fvw-gp3g-gh7f, MINI-6jcx-hrj7-7r43, MINI-74r9-rm7m-6rxw, MINI-gwmp-5qmr-pmr3, MINI-h488-6jc3-m9cv, MINI-h6fh-hj2w-8hvg, MINI-mvv3-jggm-jw96, MINI-q3xr-9fmh-m4j5, MINI-q6hf-p5h6-h95w, MINI-qp64-rrjq-xf58, MINI-qpvw-92fv-4qw8, MINI-wgwh-c67p-6wfv, MINI-wrp3-9rq7-px7c, MINI-x9h3-cq37-pw4c, ROOT-APP-NPM-CVE-2026-44291

## What is CVE-2026-44291?

CVE-2026-44291 is a high-severity code injection vulnerability in protobufjs protobuf.js, published on 13 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

protobufjs compiles protobuf definitions into JavaScript (JS) functions. Prior to 7.5.6 and 8.0.2, protobufjs used plain objects with inherited prototypes for internal type lookup tables used by generated encode and decode functions. If Object.prototype had already been polluted, those lookup tables could resolve attacker-controlled inherited properties as valid protobuf type information. This could cause attacker-controlled strings to be emitted into generated JavaScript code. This vulnerability is fixed in 7.5.6 and 8.0.2.

Weakness: CWE-94 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2026-44291?

4 open source packages ship an affected version, including protobufjs. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `protobufjs` | npm | All versions | 7.5.6 |
| `protobufjs` | npm | All versions | 7.5.6 |
| `protobufjs` | npm | From 8.0.0 | 8.0.2 |
| `protobufjs` | npm | From 8.0.0 | 8.0.2 |

Products: Protobufjs Project Protobufjs.

## How do I fix CVE-2026-44291?

Upgrade protobufjs to a fixed version for your release line: 7.5.6 or 8.0.2.

## Is CVE-2026-44291 being exploited?

There is no known exploitation of CVE-2026-44291 in the wild and no public exploit code.

## Other vulnerabilities in protobufjs protobuf.js

- [CVE-2023-36665](https://insights.sbomify.com/CVE-2023-36665/): protobufjs Prototype Pollution vulnerability (critical 9.8)
- [CVE-2026-41242](https://insights.sbomify.com/CVE-2026-41242/): protobufjs has an arbitrary code execution issue (critical 9.4)
- [CVE-2022-25878](https://insights.sbomify.com/CVE-2022-25878/): Prototype Pollution (high 8.2)
- [CVE-2026-44293](https://insights.sbomify.com/CVE-2026-44293/): protobufjs: Code injection through bytes field defaults in generated toObject code (high 7.7)
- [CVE-2026-48712](https://insights.sbomify.com/CVE-2026-48712/): protobufjs: Denial of service through unbounded Any expansion during JSON conversion (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-44291 and fix it if it is affected.

What it is: CVE-2026-44291 is a high-severity code injection vulnerability in protobufjs protobuf.js, published on 13 May 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 CVE-2026-44291 in the wild and no public exploit code.

Affected packages and fixed versions:
- protobufjs (npm): affected all versions; fixed in 7.5.6
- protobufjs (npm): affected all versions; fixed in 7.5.6
- protobufjs (npm): affected from 8.0.0; fixed in 8.0.2
- protobufjs (npm): affected from 8.0.0; fixed in 8.0.2

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-2026-44291/ (Markdown: https://insights.sbomify.com/CVE-2026-44291/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-44291
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-44291
- OSV: https://osv.dev/vulnerability/CVE-2026-44291

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-44291/
Summaries are generated and may contain mistakes; the official description above is the record.