CVE-2026-126187

CRITICALPre-NVD 9.59.5
EchelonGraph scoreMEDIUM confidence

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

This critical-severity CVE scores 9.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 1.8% (78th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Elevated

Also known asEUVD-2026-123052 (ENISA EUVD) · GHSA-xqc2-xf4c-x3h3 (GitHub Security Advisories)Source: ENISA EUVD

9.5EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • Public exploit or proof-of-concept code is available
CISA-KEV: Not listedEPSS PROB: 1.8%CVSS: 9.5Exploit: Public PoCExposed services: Not assessed

A fix is available — apply it.

React is a JavaScript library for building user interfaces. From 19.0.0 until 19.0.9, 19.1.10, 19.2.9, and 19.3.1, the react-server-dom-webpack, react-server-dom-parcel, and react-server-dom-turbopack packages are vulnerable to unauthenticated remote code execution through crafted payloads targeting frameworks that support React Server Components. The vulnerability only affects extremely rare cases where responses transport multiple typed arrays and an attacker-controlled value. Applications whose React code does not use a server are not affected. Applications that do not use a framework, bundler, or bundler plugin that supports React Server Components are not affected. This issue is fixed in versions 19.0.9, 19.1.10, 19.2.9, and 19.3.1.

CVSS
9.5
EG Score
9.5CRITICALmedium confidence
EG Risk
59
EG Risk 59/100

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)
Severity95% × 45%
Impact severity (EG Severity): CVSS 9.5 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 BOD 26-04 default: no one has published Automatable for this CVE, and CISA treats it as “no” for a CVE not in KEV.
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CVSS v4.0 confidentiality and integrity impact both High). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from 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
1.8%
EPSS %ILE
78th
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 (9.5): severity, escalated by confirmed exploitation. This CVE's 9.5 is its impact severity (EG Severity), not escalated.

EG Severity
9.5 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source
EG Likelihood
1.8% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-12). 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 (exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CVSS v4.0 confidentiality and integrity impact both High). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from 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's BOD 26-04 default) · Technical impact total (CVSS v4.0 confidentiality and integrity impact both High). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” 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

November 10, 2026

Last Modified

November 12, 2026

Advisory Details (10)

Auto-updated Nov 10, 2026
Patch available. Sources: github, github_commit, github_pr.
GitHub commit Patch Available

commit 611d9217df39 (react/react)

Patch available: react/react v19.0.9 (contains commit 611d9217df39)

https://github.com/react/react/commit/611d9217df39cf7b8ac91b2e41fd00555923e904
GitHub commit Patch Available

commit 3d06b4005ac0 (react/react)

Patch available: react/react v19.2.9 (contains commit 3d06b4005ac0)

https://github.com/react/react/commit/3d06b4005ac0cf9dec37267f26174adfe6d83611
GitHub commit Patch Available

commit 249ac87b0dad (react/react)

Patch available: react/react v19.1.10 (contains commit 249ac87b0dad)

https://github.com/react/react/commit/249ac87b0dadea4ba024d1393e5cb60cf1186080
GitHub commit

commit 0c9913ae8728 (react/react)

Fix landed in react/react commit 0c9913ae8728 — awaiting tagged release

https://github.com/react/react/commit/0c9913ae87283f96e868a8f1c20a3389827632d0
GitHub pull request

[Flight] Improve transport protocol

Fix merged in react/react PR #37846 on 2026-10-14 — awaiting tagged release

https://github.com/react/react/pull/37846
GitHub pull request Patch Available

[19.3.x][Flight] Improve transport protocol

Patch available: react/react v19.3.1 (PR #37845 merged 2026-10-14)

https://github.com/react/react/pull/37845
GitHub pull request Patch Available

[19.2.x][Flight] Improve transport protocol

Patch available: react/react v19.2.9 (PR #37844 merged 2026-10-14)

https://github.com/react/react/pull/37844
GitHub pull request Patch Available

[19.1.x][Flight] Improve transport protocol

Patch available: react/react v19.1.10 (PR #37843 merged 2026-10-14)

https://github.com/react/react/pull/37843
GitHub pull request Patch Available

[19.0.x][Flight] Improve transport protocol

Patch available: react/react v19.0.9 (PR #37842 merged 2026-10-14)

https://github.com/react/react/pull/37842
GitHub advisoryMentions a patch (unverified)

Unauthenticated Remote Code Execution in React Server Components · Advisory · react/react · GitHub

https://github.com/react/react/security/advisories/GHSA-xqc2-xf4c-x3h3

Vendor Advisories for CVE-2026-126187(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(4)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
npmreact-server-dom-parcel @ 19.0.9 (fixes >= 19.0.0, < 19.0.9)—ghsa
npmreact-server-dom-parcel @ 19.1.10 (fixes >= 19.1.0, < 19.1.10)—ghsa
npmreact-server-dom-parcel @ 19.2.9 (fixes >= 19.2.0, < 19.2.9)—ghsa
npmreact-server-dom-parcel @ 19.3.1 (fixes >= 19.3.0, < 19.3.1)—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

(3 across 1 ecosystem)
npm(3)
PackageVulnerable rangeFix by version rangeDependents
react-server-dom-parcel—
  • 19.0.0 up to 19.0.9: fixed in 19.0.9
  • 19.1.0 up to 19.1.10: fixed in 19.1.10
  • 19.2.0 up to 19.2.9: fixed in 19.2.9
  • 19.3.0 up to 19.3.1: fixed in 19.3.1
—
react-server-dom-turbopack—
  • 19.0.0 up to 19.0.9: fixed in 19.0.9
  • 19.1.0 up to 19.1.10: fixed in 19.1.10
  • 19.2.0 up to 19.2.9: fixed in 19.2.9
  • 19.3.0 up to 19.3.1: fixed in 19.3.1
—
react-server-dom-webpack—
  • 19.0.0 up to 19.0.9: fixed in 19.0.9
  • 19.1.0 up to 19.1.10: fixed in 19.1.10
  • 19.2.0 up to 19.2.9: fixed in 19.2.9
  • 19.3.0 up to 19.3.1: fixed in 19.3.1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 11× 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 → 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 22:28 UTCEchelonGraph re-scored
  2. 2026-11-12 22:28 UTCGHSA enrichmentGHSA-xqc2-xf4c-x3h3 · GitHub severity CRITICAL
  3. 2026-11-12 16:33 UTCEPSS rescoreEPSS 1.8% · 78th percentile
  4. 2026-11-12 16:25 UTCGHSA enrichmentGHSA-xqc2-xf4c-x3h3 · GitHub severity CRITICAL
  5. 2026-11-11 16:43 UTCEchelonGraph re-scored
  6. 2026-11-11 16:43 UTCGHSA enrichmentGHSA-xqc2-xf4c-x3h3 · GitHub severity CRITICAL
  7. 2026-11-11 16:38 UTCEPSS rescoreEPSS 1.8% · 78th percentile
  8. 2026-11-11 16:25 UTCEchelonGraph re-scored
  9. 2026-11-11 16:25 UTCGHSA enrichmentGHSA-xqc2-xf4c-x3h3 · GitHub severity CRITICAL
  10. 2026-11-11 02:41 UTCGHSA enrichmentGHSA-xqc2-xf4c-x3h3 · GitHub severity CRITICAL
  11. 2026-11-10 23:28 UTCEchelonGraph re-scored
  12. 2026-11-10 23:28 UTCGHSA enrichmentGHSA-xqc2-xf4c-x3h3 · GitHub severity CRITICAL
  13. 2026-11-10 23:00 UTCENISA EUVD ID recordedEUVD-2026-123052 · Source: ENISA EUVD
  14. 2026-11-10 22:58 UTCGHSA enrichmentGHSA-xqc2-xf4c-x3h3 · GitHub severity CRITICAL
  15. 2026-11-10 22:40 UTCEchelonGraph re-scoredFirst assessed: 9.5 CRITICAL
  16. 2026-11-10 22:40 UTCMITRE cvelistV5first tracked

Publicly available exploits

(2 references)

Public exploit code is referenced for this CVE (2 GitHub PoCs). Defenders should treat patch urgency accordingly.

  • GitHub PoCTahuCryptsi/poc-cve-2026-126187-rsc-usecache-rce
    Published Nov 12, 2026

    PoC: unauth RCE via Next.js use-cache typed-array framing desync (CVE-2026-126187 / GHSA-xqc2-xf4c-x3h3) | docker compose lab

    Open source ↗
  • GitHub PoCbriskets/CVE-2026-126187-poc
    Published Nov 8, 2026

    CVE-2026-126187 Unauthenticated RCE in React Server Components - PoC and Docker lab for GHSA-xqc2-xf4c-x3h3 / GHSA-673q-mjm6-r5xr

    Open source ↗

Frequently asked(5)

What is CVE-2026-126187?
CVE-2026-126187 is a critical-severity vulnerability; its CVE record was published on November 10, 2026. React is a JavaScript library for building user interfaces. From 19.0.0 until 19.0.9, 19.1.10, 19.2.9, and 19.3.1, the react-server-dom-webpack, react-server-dom-parcel, and react-server-dom-turbopack packages are vulnerable to unauthenticated remote code execution through crafted payloads…
When was the CVE record for CVE-2026-126187 published?
The CVE record for CVE-2026-126187 was published on November 10, 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 12, 2026; the record at its source may have been updated since.
Is CVE-2026-126187 actively exploited?
CVE-2026-126187 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1.8% probability of exploitation in the next 30 days (78th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-126187?
CVE-2026-126187 has a CVSS base score of 9.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-126187?
A fix for CVE-2026-126187 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-126187 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-126187

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