CVE-2026-4800 is a high-severity (CVSS 8.1) Code Injection vulnerability in lodash. 1 public exploit reference exists, so weaponization risk is real. A fix is available for lodash — see the affected versions and patch details below.
lodash vulnerable to Code Injection via `_.template` imports key names
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-4800.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-4800 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
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.
lodashnpmlodash-esnpmlodash.templatenpmDescription
Impact:
The fix for CVE-2021-23337 (https://github.com/advisories/GHSA-35jh-r3h4-6jhm) added validation for the variable option in _.template but did not apply the same validation to options.imports key names. Both paths flow into the same Function() constructor sink.
When an application passes untrusted input as options.imports key names, an attacker can inject default-parameter expressions that execute arbitrary code at template compilation time.
Additionally, _.template uses assignInWith to merge imports, which enumerates inherited properties via for..in. If Object.prototype has been polluted by any other vector, the polluted keys are copied into the imports object and passed to Function().
Patches:
Users should upgrade to version 4.18.0.
Workarounds:
Do not pass untrusted input as key names in options.imports. Only use developer-controlled, static key names.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | lodash | all versions | 4.17.21npm install lodash@4.17.21 |
| 📦npm | lodash-es | all versions | 4.17.21npm install lodash-es@4.17.21 |
| 📦npm | lodash.template | all versions | No fix |
| 📦npm | lodash-template | all versions | No fix |
| 💎RubyGems | lodash-rails | all versions | 4.17.21bundle update lodash-rails --conservative |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for lodash, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update lodash to 4.17.21 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-4800 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-4800 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-4800. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
In the context of Red Hat Enterprise Linux, the grafana and grafana-pcp packages execute the affected JavaScript entirely client-side within the user's browser. Consequently, the attack surface is strictly restricted to the local browser environment.
| Product | Fixed in | Advisory |
|---|---|---|
| Cryostat 4 on RHEL 9 | cryostat/cryostat-openshift-console-plugin-rhel9:4.2.0-9 | RHSA-2026:17789 |
| Red Hat Ansible Automation Platform 2.5 for RHEL 8 | automation-gateway-0:2.5.20260715-1.el8ap | RHSA-2026:42078 |
| Red Hat Ansible Automation Platform 2.6 for RHEL 9 | automation-platform-ui-0:2.6.9-1.el9ap | RHSA-2026:24762 |
| Red Hat Data Grid 8.6.1 | lodash | RHSA-2026:22619 |
| Red Hat Enterprise Linux 10 | pcs-0:0.12.1-1.el10_1.3 | RHSA-2026:10713 |
| Red Hat Enterprise Linux 10 | pcs-0:0.12.2-3.el10_2.1 | RHSA-2026:19008 |
| Red Hat Enterprise Linux 10 | cockpit-image-builder-0:94.3-1.el10_2 | RHSA-2026:24331 |
| Red Hat Enterprise Linux 10.0 Extended Update Support | pcs-0:0.12.0-3.el10_0.5 | RHSA-2026:11470 |
Frequently Asked Questions
Is CVE-2026-4800 in your dependencies?
O3 Security finds CVE-2026-4800 across npm, RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.