CVE-2026-23527

HIGHNVD 8.98.9—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.9 under NVD CVSS v3. EPSS exploit probability: 0.6%, top 56% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
8.9
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 8.9Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

H3 is a minimal H(TTP) framework built for high performance and portability. Prior to 1.15.5, there is a critical HTTP Request Smuggling vulnerability. readRawBody is doing a strict case-sensitive check for the Transfer-Encoding header. It explicitly looks for "chunked", but per the RFC, this header should be case-insensitive. This vulnerability is fixed in 1.15.5.

CVSS v3
8.9
EG Score
8.9(medium)
EG Risk
40(Track)
EG Risk 40/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity89% × 45%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
44.0%
KEV
Not listed

Published

January 15, 2026

Last Modified

April 13, 2026

Advisory Details (4)

Auto-updated May 21, 2026
Patch available. Sources: github.
generic

CVE-2026-23527: One Uppercase Letter Breaks Every Nuxt App | Simon Koeck

https://simonkoeck.com/writeups/h3-transfer-encoding-request-smuggling
github Patch Available

Request Smuggling (TE.TE) in h3 v1 · Advisory · h3js/h3 · GitHub

https://github.com/h3js/h3/security/advisories/GHSA-mp2g-9vg9-f4cg
generic

Release v1.15.5 · h3js/h3 · GitHub

https://github.com/h3js/h3/releases/tag/v1.15.5
generic

fix(readRawBody): fix case-sensitive `Transfer-Encoding` check causin… · h3js/h3@618ccf4 · GitHub

https://github.com/h3js/h3/commit/618ccf4f37b8b6148bea7f36040471af45bfb097

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
h3—1.15.5—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 51× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. 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. Most recent first.

Showing the most recent 100 of 120 total refreshes for this CVE.

  1. 2026-07-23 03:07 UTCEG score recompute
  2. 2026-07-22 14:08 UTCEPSS rescore
  3. 2026-07-21 15:24 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2026-23527?
CVE-2026-23527 is a high vulnerability published on January 15, 2026. H3 is a minimal H(TTP) framework built for high performance and portability. Prior to 1.15.5, there is a critical HTTP Request Smuggling vulnerability. readRawBody is doing a strict case-sensitive check for the Transfer-Encoding header. It explicitly looks for "chunked", but per the RFC, this…
When was CVE-2026-23527 disclosed?
CVE-2026-23527 was first published in the National Vulnerability Database on January 15, 2026, with the most recent update on April 13, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-23527 actively exploited?
CVE-2026-23527 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 44.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-23527?
CVE-2026-23527 has a CVSS v3 base score of 8.9 (NVD).
How do I remediate CVE-2026-23527?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-23527, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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