How severe is GHSA-g9r4-xpmj-mj65?

No CVSS score has been assigned to GHSA-g9r4-xpmj-mj65 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-g9r4-xpmj-mj65?

GHSA-g9r4-xpmj-mj65 affects the following packages: handlebars (npm), handlebars (npm). Ecosystems affected: npm.

How do I fix GHSA-g9r4-xpmj-mj65?

Update handlebars to 3.0.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g9r4-xpmj-mj65 is resolved across your whole dependency graph.

How do I detect GHSA-g9r4-xpmj-mj65 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for handlebars, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-g9r4-xpmj-mj65 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is GHSA-g9r4-xpmj-mj65 actively exploited in the wild?

No public exploit code has been indexed for GHSA-g9r4-xpmj-mj65 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was GHSA-g9r4-xpmj-mj65 published, and has it been updated?

GHSA-g9r4-xpmj-mj65 was published on September 4, 2020 and was last updated on September 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

Prototype Pollution in handlebarsGHSA-g9r4-xpmj-mj65

GHSA-g9r4-xpmj-mj65 is a remote code execution vulnerability in handlebars. A fix is available for handlebars — see the affected versions and patch details below.

Published

Sep 4, 2020

Updated

Sep 10, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Sep 10, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

17Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

handlebarsnpm

50.6Mdownloads / week

Description

Versions of handlebars prior to 3.0.8 or 4.5.3 are vulnerable to prototype pollution. It is possible to add or modify properties to the Object prototype through a malicious template. This may allow attackers to crash the application or execute Arbitrary Code in specific conditions.

Recommendation

Upgrade to version 3.0.8, 4.5.3 or later.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`handlebars`	all versions	3.0.8`npm install handlebars@3.0.8`
📦npm	`handlebars`	≥ 4.0.0&&< 4.5.3	4.5.3`npm install handlebars@4.5.3`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for handlebars, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update handlebars to 3.0.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g9r4-xpmj-mj65 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Versions of `handlebars` prior to 3.0.8 or 4.5.3 are vulnerable to prototype pollution. It is possible to add or modify properties to the Object prototype through a malicious template. This may allow attackers to crash the application or execute Arbitrary Code in specific conditions. ## Recommendation Upgrade to version 3.0.8, 4.5.3 or later.

O3 Security · Impact-Aware SCA

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