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 created must be passed to _.flatten or _.isEqual. In the case of _.flatten, the vulnerability can only be exploited if it is possible for a remote client to prepare a datastructure that consists of arrays at all levels AND if no finite depth limit is passed as the second argument to _.flatten. In the case of _.isEqual, the vulnerability can only be exploited if there exists a code path in which two distinct datastructures that were submitted by the same remote client are compared using _.isEqual. For example, if a client submits data that are stored in a database, and the same client can later submit another datastructure that is then compared to the data that were saved in the database previously, OR if a client submits a single request, but its data are parsed twice, creating two non-identical but equivalent datastructures that are then compared. Exceptions originating from the call to _.flatten or _.isEqual, as a result of a stack overflow, are not being caught. This vulnerability is fixed in 1.13.8.
CVE-2026-27601
“—” beside the score: it is equal to NVD's CVSS score.
Score 5.9 from GitHub Security Advisory (severity: HIGH) published 2026-03-03. NVD baseline CVSS 5.9; sources differ by 0.0.
Also known asEUVD-2026-9341 (ENISA EUVD) · GHSA-qpx9-hpmf-5gmw (GitHub Security Advisories)Source: ENISA EUVD
- Lower severity and no public exploit yet
A fix is available — apply it.
- CVSS v3
- 5.9
- EG Score
- 5.9MEDIUMmedium confidence
- EG Risk
- 27EG Risk 27/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity59% × 45%Impact severity (EG Severity): CVSS 5.9 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation1.1% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability0% × 15%CISA's SSVC Automatable value: no (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: A fix is available. Apply it within your standard update timelines. - EPSS PROB
- 1.1%
- EPSS %ILE
- 64th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.9): severity, escalated by confirmed exploitation. This CVE's 5.9 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.9 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 1.1% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
March 3, 2026
Last Modified
June 17, 2026
Advisory Details (3)
Auto-updated Aug 4, 2026Unlimited recursion in _.flatten and _.isEqual, potential for DoS attack · Advisory · jashkenas/underscore · GitHub
Affected: version 1.13.8. Upgrading to 1.13.8 or later completely prevents exploitation.
https://github.com/jashkenas/underscore/security/advisories/GHSA-qpx9-hpmf-5gmwcommit a6e23ae96474 (jashkenas/underscore)
Fix landed in jashkenas/underscore commit a6e23ae96474 — awaiting tagged release
https://github.com/jashkenas/underscore/commit/a6e23ae9647461ec33ad9f92a2ecfc220eea0a84commit 411e222eb0ca (jashkenas/underscore)
Fix landed in jashkenas/underscore commit 411e222eb0ca — awaiting tagged release
https://github.com/jashkenas/underscore/commit/411e222eb0ca5d570cc4f6315c02c05b830ed2b4Vendor Advisories for CVE-2026-27601(4)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2026:24841Red Hat Product SecurityMedium
Red Hat Security Advisory: Red Hat Developer Hub 1.10.0 release.
- CVE-2026-27601Microsoft Security Response Center (MSRC)High
Underscore.js has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack
- RHSA-2026:13826Red Hat Product SecurityCritical
Red Hat Security Advisory: Red Hat Developer Hub 1.9.4 release.
- RHSA-2026:9742Red Hat Product SecurityCritical
Red Hat Security Advisory: Red Hat Developer Hub 1.8.6 release.
Patch Availability(4)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| redhat | rhdh/rhdh-hub-rhel9:1780930740 | 2026-06-09 | redhat |
| redhat | rhdh/rhdh-hub-rhel9:1777903262 | 2026-05-05 | redhat |
| redhat | rhdh/rhdh-hub-rhel9:1776784286 | 2026-04-22 | redhat |
| npm | underscore @ 1.13.8 (fixes <= 1.13.7) | — | ghsa |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(5 across 5 ecosystems)
Debian:11(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| underscore | 1.13.2~dfsg-1 ... 1.9.1~dfsg-4 (15 versions) |
| — |
Debian:12(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| underscore | 1.13.4~dfsg+~1.11.4-3 ... 1.13.8~dfsg+~1.13.0-1 (8 versions) |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| underscore | 1.13.4~dfsg+~1.11.4-3 ... 1.13.8~dfsg+~1.13.0-1 (8 versions) |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| underscore | 1.13.4~dfsg+~1.11.4-3 ... 1.13.7~dfsg+~1.13.0-6 (7 versions) |
| — |
npm(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| underscore | — |
| — |
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 9× in last 7d / 41× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 97 of 242 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 3 repeat rows among the latest 100 are merged into the row they repeat. The 145 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-11-01 16:34 UTCEPSS rescoreEPSS 1.1% · 64th percentile
- 2026-11-01 07:56 UTCGHSA enrichmentGHSA-qpx9-hpmf-5gmw · GitHub severity HIGH · GitHub CVSS 5.9
- 2026-11-01 07:56 UTCEG score recompute
- 2026-10-31 16:32 UTCEPSS rescoreEPSS 1.1% · 64th percentile
- 2026-10-31 00:25 UTCOSV refresh
- 2026-10-30 16:34 UTCEPSS rescoreEPSS 1.1% · 64th percentile
- 2026-10-29 16:33 UTCEPSS rescoreEPSS 1.1% · 64th percentile
- 2026-10-28 16:32 UTCEPSS rescoreEPSS 1.0% · 61st percentile
- 2026-10-27 16:31 UTCEPSS rescoreEPSS 1.0% · 61st percentile
- 2026-10-26 16:31 UTCEPSS rescoreEPSS 1.0% · 61st percentile
- 2026-10-25 16:32 UTCEPSS rescoreEPSS 1.0% · 61st percentile
- 2026-10-25 14:38 UTCEG score recompute
- 2026-10-24 16:32 UTCEPSS rescoreEPSS 1.0% · 63rd percentile
- 2026-10-23 16:31 UTCEPSS rescoreEPSS 1.0% · 63rd percentile
- 2026-10-23 04:24 UTCEG score recompute
- 2026-10-23 04:24 UTCVendor advisory
- 2026-10-22 16:34 UTCEPSS rescoreEPSS 1.0% · 63rd percentile
- 2026-10-21 16:32 UTCEPSS rescoreEPSS 1.0% · 63rd percentile
- 2026-10-20 16:32 UTCEPSS rescoreEPSS 1.0% · 63rd percentile
- 2026-10-19 16:31 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-18 16:31 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-18 03:51 UTCEG score recompute
- 2026-10-17 16:33 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-16 16:41 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-15 16:31 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
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- 2026-10-14 16:32 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-13 16:34 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-12 16:33 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-12 16:17 UTCEG score recompute
- 2026-10-11 19:59 UTCEG score recompute
- 2026-10-11 17:13 UTCEG score recompute
- 2026-10-11 14:44 UTCEG score recompute
- 2026-10-11 13:48 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-08 17:11 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-08 13:05 UTCOSV refresh
- 2026-10-07 23:47 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-06 15:17 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-05 17:42 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-04 23:21 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-03 14:25 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-10-01 19:49 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-09-30 15:03 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
- 2026-09-28 13:51 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-09-26 15:58 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-09-26 00:26 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-09-20 20:15 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-09-18 19:27 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-18 18:50 UTCOSV refresh
- 2026-09-17 19:30 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-16 14:08 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-16 05:15 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-13 16:47 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-12 15:01 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-11 14:52 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-10 09:34 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-08 22:00 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-07 16:01 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-06 13:47 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-04 05:06 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-02 14:11 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-01 13:53 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-01 04:39 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-08-30 22:04 UTCOSV refresh
- 2026-08-30 19:17 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-08-30 01:22 UTCEPSS rescoreEPSS 1.0% · 58th percentile
- 2026-08-28 21:41 UTCEPSS rescoreEPSS 1.0% · 58th percentile
- 2026-08-27 14:25 UTCEPSS rescoreEPSS 1.0% · 58th percentile
- 2026-08-26 14:46 UTCEPSS rescoreEPSS 1.0% · 58th percentile
- 2026-08-25 13:48 UTCEPSS rescoreEPSS 1.0% · 58th percentile
- 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-14 08:38 UTCEG score recompute
- 2026-08-14 08:38 UTCVendor advisory
- 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-13 00:28 UTCEG score recompute
- 2026-08-13 00:28 UTCVendor advisory
- 2026-08-12 13:50 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-11 13:42 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-11 07:56 UTCEG score recompute
- 2026-08-11 07:56 UTCVendor advisory
- 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-10 08:09 UTCEG score recompute
- 2026-08-10 08:09 UTCVendor advisory
- 2026-08-09 13:46 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-09 08:16 UTCEG score recompute
- 2026-08-09 08:16 UTCVendor advisory
- 2026-08-08 16:37 UTCEPSS rescoreEPSS 0.9% · 56th percentile
- 2026-08-07 20:10 UTCEG score recompute
- 2026-08-07 20:10 UTCVendor advisory
Related CVEs(same product + same vendor + same CWE)
Same vendor
10 shownredhat:RHSA-2026:13826
Frequently asked(5)
What is CVE-2026-27601?
When was the CVE record for CVE-2026-27601 published?
Is CVE-2026-27601 actively exploited?
What is the CVSS score of CVE-2026-27601?
How do I remediate CVE-2026-27601?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-27601
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