PatchTheCVECVE-2026-27601: Underscore.js is a utility-belt library for JavaScript
CVE-2026-27601 is a medium-severity flaw (CVSS 5.9) affecting underscore. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.flatten and _.isEqual functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial of Service (DoS) attack by triggering a stack overflow. Untrusted input must be used to create a recursive datastructure, for example using JSON.parse, with no enforced depth limit. The datastructure thus create
Why this priority
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 5.9 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | High |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 1.0% (top 39%) |
| CISA exploited list | No |
| Weakness | CWE-770 |
| Published | 2026-03-03 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-27601?
underscore: upgrade to 1.13.8. Exact commands for each OS are on this page.
Is CVE-2026-27601 being exploited?
CVE-2026-27601 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-27601 affect?
CVE-2026-27601 affects underscore. Severity is medium (CVSS 5.9). Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.flatten and _.isEqual functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial o
How urgent is CVE-2026-27601?
Priority 46/100. Public exploit reference; Remotely exploitable, no login, no user action