CVE-2019-19919: Versions of handlebars prior to 4.3.0 are vulnerable to Prototype Pollution leading to Remote Code Execution

Q: How do I fix CVE-2019-19919?

handlebars.js: downgrade or apply the listed mitigation; tenable.sc: upgrade to 5.19.0. Exact commands for each OS are on this page.

Q: Is CVE-2019-19919 being exploited?

CVE-2019-19919 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2019-19919 affect?

CVE-2019-19919 affects handlebars.js, tenable.sc. Severity is critical (CVSS 9.8). Versions of handlebars prior to 4.3.0 are vulnerable to Prototype Pollution leading to Remote Code Execution. Templates may alter an Object's __proto__ and __defineGetter__ properties, which may allow an attacker to execute arbitrary code t

Q: How urgent is CVE-2019-19919?

Priority 63/100. Critical severity; EPSS top 6%: very likely to be exploited; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEDOWNGRADEUPGRADE

CVE-2019-19919 is a critical-severity flaw (CVSS 9.8) affecting handlebars.js, tenable.sc. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Versions of handlebars prior to 4.3.0 are vulnerable to Prototype Pollution leading to Remote Code Execution. Templates may alter an Object's __proto__ and __defineGetter__ properties, which may allow an attacker to execute arbitrary code through crafted payloads.

Why this priority

Critical severity
EPSS top 6%: very likely to be exploited
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	7.1% (top 6%)
CISA exploited list	No
Weakness	CWE-1321
Published	2019-12-20
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: handlebars.js project · tenable

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2019-12-20 23:15 UTCPublished CVE record published
2026-06-17 02:27 UTCUpdated Record last modified

handlebars.js project handlebars.js DOWNGRADE

Affected: 1.0.6 · 1.0.7 · 1.0.8 · 1.0.9 · 1.0.10 · 1.0.11 · 1.0.12 · 1.1.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0.6

1. Check installed version

npm ls handlebars.js

2. No fixed release: DOWNGRADE to a release before 1.0.6

npm view handlebars.js versions npm install handlebars.js@"<1.0.6"

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

tenable tenable.sc UPGRADE

Affected: < 5.19.0

Fixed in: 5.19.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy tenable.sc || rpm -q tenable.sc || tenable.sc --version

2. UPGRADE to 5.19.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade tenable.sc

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade tenable.sc

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2019-19919?

handlebars.js: downgrade or apply the listed mitigation; tenable.sc: upgrade to 5.19.0. Exact commands for each OS are on this page.

Is CVE-2019-19919 being exploited?

CVE-2019-19919 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2019-19919 affect?

CVE-2019-19919 affects handlebars.js, tenable.sc. Severity is critical (CVSS 9.8). Versions of handlebars prior to 4.3.0 are vulnerable to Prototype Pollution leading to Remote Code Execution. Templates may alter an Object's __proto__ and __defineGetter__ properties, which may allow an attacker to execute arbitrary code t

How urgent is CVE-2019-19919?

Priority 63/100. Critical severity; EPSS top 6%: very likely to be exploited; Remotely exploitable, no login, no user action

References

← Back to latest CVEs