TI-2026-59036 Aliases CVE-2026-86250 GHSA-q5pr-72pq-83v3

h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookie

MEDIUM 44CWE-400Published 2026-09-06 · Updated 2026-09-18

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-400.

Summary

h3 versions before 2.0.1-rc.18 fail to validate the chunk count parsed from user-controlled cookie values in setChunkedCookie() and deleteChunkedCookie() functions. Attackers can send a crafted cookie header with an extremely large chunk count to trigger an O(n²) cleanup loop that hangs the server process.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00488 42nd percentileScored 2026-11-07

Fix Fixed h3 (h3js): 2.0.1-rc.18h3 (npm): 2.0.1-rc.18Red Hat: 1 advisory

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
h3js	h3	2.0.0-beta.4 to before 2.0.1-rc.18	2.0.1-rc.18	Patch available	CNA
—	h3 (npm)	2.0.0-beta.4 to before 2.0.1-rc.18	2.0.1-rc.18	Patch available	GHSA-q5pr-72pq-83v3

h3 Vendorh3js Affected 2.0.0-beta.4 to before 2.0.1-rc.18 Fixed in 2.0.1-rc.18 Patch available CNA
h3 (npm) Vendor— Affected 2.0.0-beta.4 to before 2.0.1-rc.18 Fixed in 2.0.1-rc.18 Patch available GHSA-q5pr-72pq-83v3

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:h3:h3::::::::	—	—	h3js

cpe:2.3:a:h3:h3:*:*:*:*:*:*:*:* Versions — — ·h3js

Remediation

Fix · CNA h3 (h3js) Fixed in 2.0.1-rc.18
Fix · GHSA-q5pr-72pq-83v3 h3 (npm) Fixed in 2.0.1-rc.18 Advisory →

Red Hat 1 advisory

RHSA-2026:84734 Released 2026-10-19 · Red Hat rating Critical
RHOAI 3.4.5 - Red Hat OpenShift AI
- Red Hat OpenShift AI 3.4 registry.redhat.io/rhoai/odh-ai-gateway-payload-processing-rhel9, registry.redhat.io/rhoai/odh-automl-rhel9, registry.redhat.io/rhoai/odh-autorag-rhel9 +47

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

Release · 2026-09-06
h3js h3 2.0.1-rc.18
2 records Highest priority Priority MEDIUM 2 MEDIUM
Other records, highest priority first
- TI-2026-58994 h3 before 2.0.1-rc.18 Open Redirect via redirectBack()Priority MEDIUM 57
Show all 2 records →

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

Product	Status	Plan or fix
Red Hat OpenShift AI 3.4	Fixed	RHSA-2026:84734

Not affected: 1 product

Red Hat OpenShift AI 3.4

Timeline

2026-10-02 Threatist record created from CVE-2026-86250
2026-10-03 Alias added: GHSA-q5pr-72pq-83v3
2026-10-20 Fix available: RHSA-2026:84734 · Red Hat
2026-10-20 Fix available: Red Hat OpenShift AI 3.4 · Red Hat

References

Advisory 2

Other 3

TI-2026-25559 h3 has a Server-Sent Events Injection via Unsanitized Newlines in Event Stream Fields CVSS 3.1CRITICAL 10.0
TI-2026-25562 h3 has a middleware bypass with one gadget CVSS 3.1CRITICAL 9.1
TI-2026-59038 h3 before 1.15.9 SSE Event Injection via Carriage Return CVSS 4.0MEDIUM 6.9
TI-2026-59037 h3 before 1.15.9 Path Traversal via Double Decoding CVSS 4.0HIGH 8.2
TI-2026-25560 h3 has an observable timing discrepancy in basic auth utils CVSS 3.1MEDIUM 5.9
TI-2026-58994 h3 before 2.0.1-rc.18 Open Redirect via redirectBack() CVSS 4.0MEDIUM 5.3

See all 10 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences