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GHSA-r5fr-rjxr-66jc
No affected components available
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:
- Validate
importsKeysagainst the existingreForbiddenIdentifierCharsregex (same check already used for thevariableoption) - Replace
assignInWithwithassignWithwhen 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.
The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is moderate. The vulnerability is likely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
- CVE-2026-4800
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.
Alias, EPSS 21.33% - CVE-2021-23337
Lodash versions prior to 4.17.21 are vulnerable to Command Injection via the template function.
Alias, EPSS 21.33% - EUVD-2021-0912Alias
- EUVD-2026-17610Alias
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