# CVE-2026-27837: Dottie vulnerable to prototype pollution bypass via non-first path segments in set() and transform()

> Attackers can bypass prototype pollution guards in Dottie by placing __proto__ in non-first path segments, potentially leading to code execution or privilege escalation.

- **Severity:** Medium 6.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 26 Feb 2026
- **Updated:** 26 Feb 2026
- **Also known as:** CLEANSTART-2026-BG28241, CLEANSTART-2026-TR92634, DEBIAN-CVE-2026-27837, GHSA-r5mx-6wc6-7h9w, UBUNTU-CVE-2026-27837

## What is CVE-2026-27837?

CVE-2026-27837 is a medium-severity code injection vulnerability in mickhansen dottie.js, published on 26 Feb 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Dottie provides nested object access and manipulation in JavaScript. Versions 2.0.4 through 2.0.6 contain an incomplete fix for CVE-2023-26132. The prototype pollution guard introduced in commit `7d3aee1` only validates the first segment of a dot-separated path, allowing an attacker to bypass the protection by placing `__proto__` at any position other than the first. Both `dottie.set()` and `dottie.transform()` are affected. Version 2.0.7 contains an updated fix to address the residual vulnerability.

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

## Which versions are affected by CVE-2026-27837?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `dottie` | npm | From 2.0.4 | 2.0.7 |
| `dottie` | npm | From 2.0.4 | 2.0.7 |

Products: Dottie Project Dottie.

## How do I fix CVE-2026-27837?

Upgrade dottie to 2.0.7 or later.

## Is CVE-2026-27837 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27837 exists.

## Other vulnerabilities in mickhansen dottie.js

- [CVE-2023-26132](https://insights.sbomify.com/CVE-2023-26132/): dottie vulnerable to Prototype Pollution (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27837 and fix it if it is affected.

What it is: CVE-2026-27837 is a medium-severity code injection vulnerability in mickhansen dottie.js, published on 26 Feb 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27837 exists.

Affected packages and fixed versions:
- dottie (npm): affected from 2.0.4; fixed in 2.0.7
- dottie (npm): affected from 2.0.4; fixed in 2.0.7

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-2026-27837/ (Markdown: https://insights.sbomify.com/CVE-2026-27837/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27837
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27837
- OSV: https://osv.dev/vulnerability/CVE-2026-27837

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27837/
Summaries are generated and may contain mistakes; the official description above is the record.