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CVE-2026-27601VulnerabilityPublished Updated

_.flatten · Underscore.js has unlimited recursion

Affects MicrosoftSource GCVE Database

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Authoritative record:CVE-2026-27601· High 8.2

Not known to be exploited · CVSS 8.2 High : upgrade to 1.13.8 soon.

Data as of 14 Nov 2026, 09:04 UTC

CVSS 4.0 base score
8.2High
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 1.13.8
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 3 Mar 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

What to do

Upgrade underscore to 1.13.8.

Affected software

ProductAffectedFixed in
jashkenasunderscoreAffected
  • <1.13.8
Fixed in
  • 1.13.8
npmunderscorepkg:npm/underscoreOther threatsAffected
  • <1.13.8
Fixed in
  • 1.13.8

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, avoid processing untrusted input with the affected functions or implement input validation to mitigate recursion depth.

Description

Underscore.js versions 2.0 and 3.0 contain vulnerabilities in the _.flatten and _.isEqual functions that allow unlimited recursion, which can potentially lead to denial-of-service (DoS) attacks.

References

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