Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Versions 1.4.0 through 1.4.16 contain a prototype pollution vulnerability in mergeDeep after merging results of two standard schema validations with the same key. Due to the ordering of merging, there must be an any type that is set as a standalone guard, to allow for the __proto__ prop to be merged. When combined with GHSA-8vch-m3f4-q8jf this allows for a full RCE by an attacker. This issue is fixed in version 1.4.17. To workaround, remove the __proto__ key from body.
CVE-2025-66456
“—” beside the score: it is equal to NVD's CVSS score.
This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 0.6% (46th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.
Also known asEUVD-2025-202180 (ENISA EUVD) · GHSA-hxj9-33pp-j2cc (GitHub Security Advisories)Source: ENISA EUVD
- CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
A fix is available — apply it.
- CVSS v3
- 9.8
- EG Score
- 9.8CRITICALmedium confidence
- EG Risk
- 60EG Risk 60/100
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)Severity98% × 45%Impact severity (EG Severity): CVSS 9.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation40% × 40%EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.Automatability0% × 15%CISA's SSVC Automatable value: no (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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 at low or medium mission impact and sooner than that at high. - EPSS PROB
- 0.6%
- EPSS %ILE
- 46th
- 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 (9.8): severity, escalated by confirmed exploitation. This CVE's 9.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 9.8 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
- EG Likelihood
- 0.6% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-01). 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 low, Track* at medium and Attend at high mission impact.CISA BOD 26-04: 14 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 low, Track* at medium and Attend at high mission impact.
A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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)14 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 total (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
December 9, 2025
Last Modified
October 14, 2026
Advisory Details (5)
Auto-updated Oct 30, 2026Prototype pollution with multiple standalone validation schemas · Advisory · elysiajs/elysia · GitHub
https://github.com/elysiajs/elysia/security/advisories/GHSA-hxj9-33pp-j2ccArbitrary code injection through cookie config · Advisory · elysiajs/elysia · GitHub
https://github.com/elysiajs/elysia/security/advisories/GHSA-8vch-m3f4-q8jfpatch 1.4.17
Patch available: elysiajs/elysia 1.4.17 (PR #1564 merged 2025-12-02)
https://github.com/elysiajs/elysia/pull/1564commit 3af978663e43 (elysiajs/elysia)
Patch available: elysiajs/elysia 1.4.17 (contains commit 3af978663e43)
https://github.com/elysiajs/elysia/commit/3af978663e437dccc6c1a2a3aff4b74e1574849ecommit 26935bf76ebc (elysiajs/elysia)
Patch available: elysiajs/elysia 1.4.17 (contains commit 26935bf76ebc)
https://github.com/elysiajs/elysia/commit/26935bf76ebc43b4a43d48b173fc853de43bb51ePatch Availability(1)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| npm | elysia @ 1.4.17 (fixes >= 1.4.0, < 1.4.17) | — | 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
(1 across 1 ecosystem)
npm(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| elysia | — |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 16× in last 7d / 58× 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 98 of 221 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. 2 repeat rows among the latest 100 are merged into the row they repeat. The 123 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-11-02 00:27 UTCEG score recompute
- 2026-11-02 00:27 UTCGHSA enrichmentGHSA-hxj9-33pp-j2cc · GitHub severity CRITICAL
- 2026-11-01 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-11-01 08:01 UTCGHSA enrichmentGHSA-hxj9-33pp-j2cc · GitHub severity CRITICAL
- 2026-11-01 01:53 UTCEG score recompute
- 2026-10-31 16:31 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-10-31 03:17 UTCEG score recompute
- 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-10-30 04:42 UTCEG score recompute
- 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-10-29 06:08 UTCEG score recompute
- 2026-10-28 16:30 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-10-28 07:33 UTCEG score recompute
- 2026-10-27 16:30 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-10-27 08:58 UTCEG score recompute
- 2026-10-26 16:30 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-10-26 09:04 UTCEG score recompute
- 2026-10-25 16:31 UTCEPSS rescoreEPSS 0.6% · 46th percentile
- 2026-10-25 16:08 UTCEG score recompute
- 2026-10-25 10:28 UTCEG score recompute
- 2026-10-24 16:31 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-10-24 11:53 UTCEG score recompute
- 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-10-23 13:18 UTCEG score recompute
- 2026-10-22 16:33 UTCEPSS rescoreEPSS 0.6% · 45th percentile
Show 73 moreShow fewer
- 2026-10-22 14:40 UTCEG score recompute
- 2026-10-21 16:31 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-10-20 17:08 UTCEG score recompute
- 2026-10-20 16:31 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-10-19 23:28 UTCEG score recompute
- 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-10-18 22:51 UTCEG score recompute
- 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-10-18 05:19 UTCEG score recompute
- 2026-10-18 00:15 UTCEG score recompute
- 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-10-17 01:36 UTCEG score recompute
- 2026-10-16 16:39 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-10-16 01:58 UTCEG score recompute
- 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-10-14 21:26 UTCEG score recompute
- 2026-10-14 16:31 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-10-14 03:14 UTCEG score recompute
- 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-10-12 16:48 UTCEG score recompute
- 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-10-11 20:23 UTCEG score recompute
- 2026-10-11 18:35 UTCEG score recompute
- 2026-10-11 15:09 UTCEG score recompute
- 2026-10-11 13:47 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-10-10 19:59 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-10-09 20:06 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-10-08 17:10 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-10-04 23:21 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-10-03 20:51 UTCOSV refresh
- 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-10-01 19:49 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-30 15:02 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-29 15:20 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-28 13:50 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-24 14:02 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-23 13:47 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-19 15:42 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-18 19:27 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-17 19:30 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-16 14:07 UTCEPSS rescoreEPSS 0.6% · 45th percentile
- 2026-09-15 03:10 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-14 10:50 UTCOSV refresh
- 2026-09-13 16:46 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-12 15:00 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-11 14:52 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-11 09:36 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-07 16:00 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.6% · 44th percentile
- 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-09-02 14:11 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-30 19:16 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-30 01:21 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-28 21:40 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-27 14:24 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-26 14:45 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-26 12:02 UTCOSV refresh
- 2026-08-25 13:48 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-24 14:16 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-23 00:18 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-21 23:48 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-18 13:47 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-08-17 13:46 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
Related CVEs(same product + same CWE)
Same product
4 shownnpm:elysia
Frequently asked(5)
What is CVE-2025-66456?
When was the CVE record for CVE-2025-66456 published?
Is CVE-2025-66456 actively exploited?
What is the CVSS score of CVE-2025-66456?
How do I remediate CVE-2025-66456?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2025-66456
Is Your Infrastructure Affected by CVE-2025-66456?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.