TI-2026-60307 Aliases CVE-2026-88975 GHSA-gq9p-f254-h286

Http4s: Ember HTTP/2 buffers a frame's declared payload before checking SETTINGS_MAX_FRAME_SIZE

MEDIUM 40CWE-400Published 2026-09-15 · Updated 2026-09-16

Key facts

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

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-400.

Summary

Http4s is a Scala interface for HTTP services. Prior to 0.23.37 and 1.0.0-M48, Ember’s HTTP/2 read loop parses a frame’s 24-bit declared length but waits to buffer the entire payload before comparing it with SETTINGS_MAX_FRAME_SIZE. An unauthenticated peer can declare a payload near 16 MiB on a connection where Ember advertised 16 KiB and either complete or slowly stream it, causing up to 1024-fold memory amplification per connection before processFrame can reject the frame. The shared H2Connection.readLoop affects withHttp2 servers and clients, while HTTP/2-disabled configurations are unaffected, and the patch rejects oversized frames before buffering their payloads. This issue is fixed in versions 0.23.37 and 1.0.0-M48.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.0063 50th percentileScored 2026-11-07

Fix Fixed http4s (http4s): 0.23.37, 1.0.0-M48org.http4s:http4s-ember-core_2.13 (Maven): 0.23.37, 1.0.0-M48+2 more products

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
http4s	http4s	before 0.23.37; 1.0.0-M1 to before 1.0.0-M48	0.23.37, 1.0.0-M48	Patch available	CNA
—	org.http4s:http4s-ember-core_2.13 (Maven)	before 0.23.37	0.23.37	Patch available	GHSA-gq9p-f254-h286
—	org.http4s:http4s-ember-core_2.12 (Maven)	before 0.23.37	0.23.37	Patch available	GHSA-gq9p-f254-h286
—	org.http4s:http4s-ember-core_3 (Maven)	before 0.23.37	0.23.37	Patch available	GHSA-gq9p-f254-h286
—	org.http4s:http4s-ember-core_2.13 (Maven)	1.0.0-M1 to before 1.0.0-M48	1.0.0-M48	Patch available	GHSA-gq9p-f254-h286
—	org.http4s:http4s-ember-core_3 (Maven)	1.0.0-M1 to before 1.0.0-M48	1.0.0-M48	Patch available	GHSA-gq9p-f254-h286

http4s Vendorhttp4s Affected before 0.23.37; 1.0.0-M1 to before 1.0.0-M48 Fixed in 0.23.37, 1.0.0-M48 Patch available CNA
org.http4s:http4s-ember-core_2.13 (Maven) Vendor— Affected before 0.23.37 Fixed in 0.23.37 Patch available GHSA-gq9p-f254-h286
org.http4s:http4s-ember-core_2.12 (Maven) Vendor— Affected before 0.23.37 Fixed in 0.23.37 Patch available GHSA-gq9p-f254-h286
org.http4s:http4s-ember-core_3 (Maven) Vendor— Affected before 0.23.37 Fixed in 0.23.37 Patch available GHSA-gq9p-f254-h286
org.http4s:http4s-ember-core_2.13 (Maven) Vendor— Affected 1.0.0-M1 to before 1.0.0-M48 Fixed in 1.0.0-M48 Patch available GHSA-gq9p-f254-h286
org.http4s:http4s-ember-core_3 (Maven) Vendor— Affected 1.0.0-M1 to before 1.0.0-M48 Fixed in 1.0.0-M48 Patch available GHSA-gq9p-f254-h286

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:typelevel:http4s::::::::	—	—	http4s

cpe:2.3:a:typelevel:http4s:*:*:*:*:*:*:*:* Versions — — ·http4s

Remediation

Fix · CNA http4s (http4s) Fixed in 0.23.37, 1.0.0-M48
Fix · GHSA-gq9p-f254-h286 org.http4s:http4s-ember-core_2.13 (Maven) Fixed in 0.23.37 Advisory →
Fix · GHSA-gq9p-f254-h286 org.http4s:http4s-ember-core_2.12 (Maven) Fixed in 0.23.37 Advisory →
Fix · GHSA-gq9p-f254-h286 org.http4s:http4s-ember-core_3 (Maven) Fixed in 0.23.37 Advisory →
Fix · GHSA-gq9p-f254-h286 org.http4s:http4s-ember-core_2.13 (Maven) Fixed in 1.0.0-M48 Advisory →
Fix · GHSA-gq9p-f254-h286 org.http4s:http4s-ember-core_3 (Maven) Fixed in 1.0.0-M48 Advisory →

Timeline

2026-10-02 Threatist record created from CVE-2026-88975
2026-10-03 Alias added: GHSA-gq9p-f254-h286
2026-10-28 EPSS moved to the 50th–90th percentile

References

Other 5

TI-2022-13223 mTLS client verification is skipped in fs2 on Node.js CVSS 3.1CRITICAL 9.8
TI-2023-08714 Http4s has fatal error parsing User-Agent and Server headers CVSS 3.1HIGH 7.5
TI-2022-06031 Hash collision in typelevel jawn CVSS 3.1HIGH 7.5
TI-2025-37261 Http4s vulnerable to HTTP Request Smuggling due to improper handling of HTTP trailer section CVSS 4.0MEDIUM 6.3
TI-2026-44185 http4s-scala-xml has an XML External Entity (XXE) processing issue CVSS 3.1CRITICAL 9.3
TI-2020-04336 Local file inclusion vulnerability in http4s CVSS 3.1HIGH 7.6

See all 36 →

Sources

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