# CVE-2026-106445: Handlebars: JavaScript Injection via Own Property Check Bypass

> Attackers can execute arbitrary JavaScript by bypassing prototype checks in Handlebars templates when specific configuration options are enabled.

- **Severity:** Critical 9.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Oct 2026
- **Updated:** 12 Oct 2026
- **Also known as:** CLEANSTART-2026-HT67840, CLSA-2026-1791679650, CLSA-2026-1791827421, DEBIAN-CVE-2026-106445, ECHO-99e3-a778-74df, GHSA-p8wg-vrv2-v86f, MINI-39gf-jwx3-wqpx, MINI-fjh5-38xg-q8g3, MINI-g662-v44x-f66x, MINI-gxgv-x9fp-9hq2, MINI-j3p5-vmc7-86cg, MINI-j72r-gh3h-6rx4, MINI-jgjp-9j8p-jm58, MINI-mp9p-gm44-fqvp, MINI-qm78-m7p4-4754, MINI-w5m8-4672-p8hg, MINI-wrxp-4w63-jppq, ROOT-APP-NPM-CVE-2026-106445, UBUNTU-CVE-2026-106445

## What is CVE-2026-106445?

CVE-2026-106445 is a critical code injection vulnerability in handlebars-lang handlebars.js, published on 6 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Handlebars provides the power necessary to let users build semantic templates. From 3.0.0 until 4.7.10, Handlebars lookupProperty returns Function.prototype.constructor before applying the prototype-access deny list because constructor is an own property of Function.prototype. When an attacker can render a controlled template with allowProtoMethodsByDefault enabled and an accessible function in the template context, the template can traverse from that function through its prototype to Function.prototype and then obtain the Function constructor through the own-property bypass. This permits attacker-controlled JavaScript to execute with the server application's privileges. This issue is fixed in version 4.7.10.

Weakness: CWE-184 (Incomplete List of Disallowed Inputs), CWE-1289 (Improper Validation of Unsafe Equivalence in Input)

## Which versions are affected by CVE-2026-106445?

2 open source packages ship an affected version, including handlebars.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `handlebars` | npm | From 3.0.0 | 4.7.10 |
| `handlebars` | npm | From 3.0.0 | 4.7.10 |

## How do I fix CVE-2026-106445?

Upgrade handlebars to 4.7.10 or later.

## Is CVE-2026-106445 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-106445 exists.

Public exploit code:

- CVE-2026-106445 — Handlebars 4.0.0–4.7.9 RCE via Function.prototype.constructor bypass (GHSA-p8wg-vrv2-v86f). PoCbit PoC + Docker lab (4.7.9), check/exploit HTTP client, GHSA template chain. Fixed 4.7.10. https://pocbit.org/pocs/cve-2026-106445 (github_poc): https://github.com/murrez/CVE-2026-106445

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-106445 and fix it if it is affected.

What it is: CVE-2026-106445 is a critical code injection vulnerability in handlebars-lang handlebars.js, published on 6 Oct 2026. 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-2026-106445 exists.

Affected packages and fixed versions:
- handlebars (npm): affected from 3.0.0; fixed in 4.7.10
- handlebars (npm): affected from 3.0.0; fixed in 4.7.10

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-2026-106445/ (Markdown: https://insights.sbomify.com/CVE-2026-106445/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-106445
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-106445
- OSV: https://osv.dev/vulnerability/CVE-2026-106445

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-106445/
Summaries are generated and may contain mistakes; the official description above is the record.