CVE-2026-63402

MEDIUMPre-NVD 5.95.9
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 5.9 under the CNA's CVSS (NVD's own analysis pending). EPSS exploit probability: 0.3% (18th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from the CNA's CVSS
Sources: the CNA's CVSS, EPSS
Elevated

Also known asEUVD-2026-114546 (ENISA EUVD)Source: ENISA EUVD

5.9EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.9Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

i18next is an internationalization framework for JavaScript. Prior to version 26.3.4, deepExtend in src/utils.js checks property existence with the in operator and recurses into inherited built-ins reached through Object.prototype. An application must explicitly pass attacker-controlled resource data to addResourceBundle(lng, ns, data, deep, overwrite) with both deep: true and overwrite: true. Source keys such as hasOwnProperty, toString and valueOf can then select shared inherited built-in function objects, and a nested value can overwrite a property of those objects process-wide. For example, making Object.prototype.hasOwnProperty.call non-callable causes subsequent uses, including i18next internals, to throw TypeError, resulting in unrecoverable denial of service and limited integrity impact. The __proto__/constructor guard does not prevent this mechanism because the corruption target is an inherited built-in function rather than the prototype object itself. Default calls without deep merging or with overwrite falsy are unaffected, and no standard i18next backend or integration uses the vulnerable configuration. This issue is distinct from the setPath/key-walking prototype-pollution flaws in i18next-fs-backend (CVE-2026-48713) and i18next-http-middleware (CVE-2026-48714). This issue is fixed in version 26.3.4.

CVSS v3
5.9
EG Score
5.9MEDIUMmedium confidence
EG Risk
43
EG Risk 43/100

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.
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 or medium mission impact; Track* at high (mission-essential systems).
Exploitation public PoC (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
0.3%
EPSS %ILE
18th
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.the CNA's CVSS · CVSS v3.0 or v3.1
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-04). 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 or medium mission impact; Track* at high (mission-essential systems).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 low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation public PoC (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

October 30, 2026

Last Modified

November 5, 2026

Advisory Details (3)

Auto-updated Oct 30, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_commit.
Web page

GitHub - i18next/i18next at v26.3.4 · GitHub

https://github.com/i18next/i18next/tree/v26.3.4
GitHub commit Patch Available

commit 642137b7786d (i18next/i18next)

Patch available: i18next/i18next v26.3.4 (contains commit 642137b7786d)

https://github.com/i18next/i18next/commit/642137b7786d83661ec3ee53027798dc4b81d30a
GitHub advisoryMentions a patch (unverified)🟡 PoC Available

i18next deepExtend recurses into inherited built-ins, allowing corruption of shared built-in objects (DoS) · Advisory · i18next/i18next · GitHub

https://github.com/i18next/i18next/security/advisories/GHSA-6jcc-5g8w-32mx

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
node-i18next22.4.8-1, 23.7.6-1, 23.7.6-2, 26.7.1-1
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
node-i18next23.7.6-1, 23.7.6-2, 26.7.1-1
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
node-i18next23.7.6-1, 23.7.6-2
  • every version up to 26.7.1-1: fixed in 26.7.1-1
—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 15× 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 its CVE.org record (CNA or CISA ADP). 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). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

  1. 2026-11-12 16:34 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  2. 2026-11-11 16:40 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  3. 2026-11-10 16:45 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  4. 2026-11-09 16:35 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  5. 2026-11-08 16:40 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  6. 2026-11-07 16:39 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  7. 2026-11-06 16:39 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  8. 2026-11-05 16:38 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  9. 2026-11-05 03:26 UTCEchelonGraph re-scored
  10. 2026-11-05 03:04 UTCEchelonGraph re-scored
  11. 2026-11-04 16:36 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  12. 2026-11-03 16:48 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  13. 2026-11-02 19:28 UTCEchelonGraph re-scored
  14. 2026-11-02 16:45 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  15. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  16. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  17. 2026-10-31 00:02 UTCENISA EUVD ID recordedEUVD-2026-114546 · Source: ENISA EUVD
  18. 2026-10-30 23:26 UTCEchelonGraph re-scored
  19. 2026-10-30 22:49 UTCEchelonGraph re-scoredFirst assessed: 5.9 MEDIUM
  20. 2026-10-30 22:48 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-63402?
CVE-2026-63402 is a medium-severity vulnerability; its CVE record was published on October 30, 2026. i18next is an internationalization framework for JavaScript. Prior to version 26.3.4, deepExtend in src/utils.js checks property existence with the in operator and recurses into inherited built-ins reached through Object.prototype. An application must explicitly pass attacker-controlled resource…
When was the CVE record for CVE-2026-63402 published?
The CVE record for CVE-2026-63402 was published on October 30, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of November 5, 2026; the record at its source may have been updated since.
Is CVE-2026-63402 actively exploited?
CVE-2026-63402 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (18th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-63402?
CVE-2026-63402 has a CVSS base score of 5.9 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-63402?
A fix for CVE-2026-63402 is available: update to the fixed version the vendor names in its advisory.

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