TI-2026-58994 Aliases CVE-2026-86205 GHSA-vhx4-2r84-67h4

h3 before 2.0.1-rc.18 Open Redirect via redirectBack()

MEDIUM 57CWE-601Published 2026-09-06 · Updated 2026-09-08

Key facts

Attack vector: Network
Privileges required: None
User interaction: Passive
Attack complexity: Low
Attack requirements: None
Impact type: Spoofing
Confidentiality · integrity · availability: Low · Low · None
Fix status: Partial Red Hat: 1 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-601.

Summary

h3 versions before 2.0.1-rc.18 contain an open redirect vulnerability in the redirectBack() utility that fails to sanitize protocol-relative paths in the Referer header pathname. Attackers can craft a same-origin URL with a double-slash path segment that passes origin validation but produces a Location header interpreted by browsers as a protocol-relative redirect to an external domain.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00271 19th percentileScored 2026-11-07

Fix Partial h3 (h3js): 2.0.1-rc.18Red Hat: 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: No
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	2.0.1-rc.17 to before 2.0.1-rc.18	2.0.1-rc.18	Patch available	CNA

h3 Vendorh3js Affected 2.0.1-rc.17 to before 2.0.1-rc.18 Fixed in 2.0.1-rc.18 Patch available CNA

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

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-2026-59036 h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked CookiePriority MEDIUM 44
Show all 2 records →

Vendor assessments

Red Hat

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

Product	Status	Plan or fix
Red Hat OpenShift AI (RHOAI)	Affected	No fix yet: Fix deferred

Timeline

2026-10-02 Threatist record created from CVE-2026-86205
2026-10-03 Alias added: GHSA-vhx4-2r84-67h4

References

Advisory 1

GitHub Security Advisory (GHSA-fp4x-ggrf-wmc6)

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-2026-25886 h3: Missing Path Segment Boundary Check in `mount()` Causes Middleware Execution on Unrelated Prefix-Matching Routes CVSS 3.1MEDIUM 5.3

See all 10 →

Sources

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