CVE-2026-4800

ADVISORY - github

Summary

Impact

The fix for CVE-2021-23337 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.

The fix applies two changes:

  1. Validate importsKeys against the existing reForbiddenIdentifierChars regex (same check already used for the variable option)
  2. Replace assignInWith with assignWith when merging imports, so only own properties are enumerated

Workarounds

Do not pass untrusted input as key names in options.imports. Only use developer-controlled, static key names.

EPSS Score: 0.00068 (0.211)

Common Weakness Enumeration (CWE)

ADVISORY - nist

Improper Control of Generation of Code ('Code Injection')

ADVISORY - github

Improper Control of Generation of Code ('Code Injection')

ADVISORY - redhat

Improper Control of Generation of Code ('Code Injection')


GitHub

CREATED

UPDATED

EXPLOITABILITY SCORE

2.2

EXPLOITS FOUND
-
COMMON WEAKNESS ENUMERATION (CWE)

CVSS SCORE

8.1high
PackageTypeOS NameOS VersionAffected RangesFix Versions
lodashnpm-->=4.0.0,<=4.17.234.18.0
lodash-amdnpm-->=4.0.0,<=4.17.234.18.0
lodash-esnpm-->=4.0.0,<=4.17.234.18.0
lodash.templatenpm-->=4.0.0,<4.18.04.18.0

CVSS:3 Severity and metrics

The CVSS metrics represent different qualitative aspects of a vulnerability that impact the overall score, as defined by the CVSS Specification.

The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone). One example of an Adjacent attack would be an ARP (IPv4) or neighbor discovery (IPv6) flood leading to a denial of service on the local LAN segment (e.g., CVE-2013-6014).

A successful attack depends on conditions beyond the attacker's control, requiring investing a measurable amount of effort in research, preparation, or execution against the vulnerable component before a successful attack.

The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.

The vulnerable system can be exploited without interaction from any user.

An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.

There is a total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.

There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any or all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.

There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component.

NIST

CREATED

UPDATED

ADVISORY IDCVE-2026-4800
EXPLOITABILITY SCORE

2.2

EXPLOITS FOUND
-
COMMON WEAKNESS ENUMERATION (CWE)

CVSS SCORE

8.1high

Debian

CREATED

UPDATED

ADVISORY IDCVE-2026-4800
EXPLOITABILITY SCORE

-

EXPLOITS FOUND
-
COMMON WEAKNESS ENUMERATION (CWE)-
RATING UNAVAILABLE FROM ADVISORY

Ubuntu

CREATED

UPDATED

ADVISORY IDCVE-2026-4800
EXPLOITABILITY SCORE

-

EXPLOITS FOUND
-
COMMON WEAKNESS ENUMERATION (CWE)-

CVSS SCORE

N/Amedium

Red Hat

CREATED

UPDATED

ADVISORY IDCVE-2026-4800
EXPLOITABILITY SCORE

2.2

EXPLOITS FOUND
-
COMMON WEAKNESS ENUMERATION (CWE)

CVSS SCORE

8.1high

Chainguard

CREATED

UPDATED

ADVISORY ID

CGA-738g-g4gp-hqw4

EXPLOITABILITY SCORE

-

EXPLOITS FOUND
-
COMMON WEAKNESS ENUMERATION (CWE)-
RATING UNAVAILABLE FROM ADVISORY

minimos

CREATED

UPDATED

ADVISORY ID

MINI-cf3v-8g9p-ccgg

EXPLOITABILITY SCORE

-

EXPLOITS FOUND
-
COMMON WEAKNESS ENUMERATION (CWE)-
RATING UNAVAILABLE FROM ADVISORY