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Vulnerabilities

Vulnerability · CVE-2026-35209

defu is software that allows uers to assign default properties recursively.

Published Apr 6, 2026 · catalog updated Jul 21, 2026 · defu is software that

Check if you run it

No confirmed exploitation is on record for CVE-2026-35209. EPSS is 0.52%. Act only if a listed version of defu is software that is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (defu is software that).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.52%
Remediation
Advisory link
Affected products
cpe unjs/defu

defu is software that allows uers to assign default properties recursively. Prior to version 6.1.5, applications that pass unsanitized user input (e.g. parsed JSON request bodies, database records, or config files from untrusted sources) as the first argument to are vulnerable to prototype pollution. A crafted payload containing a key can override intended default values in the merged resul. The internal function used to copy the defaults object. invokes the setter, which replaces the resulting object's with attacker-controlled values. Properties inherited from the polluted prototype then bypass the existing key guard in the loop and land in the final result. Version 6.1.5 replaces with object spread ( ), which uses and does not invoke the setter.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe unjs/defuversion unspecified

How to fix CVE-2026-35209

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-35209. EPSS is 0.52%. Act only if a listed version of defu is software that is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-1321: Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). EPSS 0.52%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Apr 6, 2026 · NIST NVD

    Detected

    defu is software that allows uers to assign default properties recursively. Prior to version 6.1.5, applications that pass unsanitized user input (e.g. parsed JSON request bodies, database records, or config files from untrusted sources) as the first argument to are vulnerable to prototype pollution. A crafted payload containing a key can override intended default values in the merged resul. The i

  2. Jul 21, 2026 · NIST NVD

    Updated

    defu is software that allows uers to assign default properties recursively. Prior to version 6.1.5, applications that pass unsanitized user input (e.g. parsed JSON request bodies, database records, or config files from untrusted sources) as the first argument to are vulnerable to prototype pollution. A crafted payload containing a key can override intended default values in the merged resul. The i

Sources

  • CVE.orgVulnerability recordCVE-2026-35209

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-35209

    30-day exploitation probability 0.5%

    first.org
  • NIST NVDVulnerability recordCVE-2026-35209

    defu is software that allows uers to assign default properties recursively. Prior to version 6.1.5, applications that pass unsanitized user input (e.g. parsed JSON request bodies, database records, or config files from untrusted sources) as the first argument to are vuln

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.