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Fencer Vulns
high 7.5

CVE-2026-88975 json

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

published 2026-09-15 54 d ago modified 2026-09-16 53 d ago also EUVD-2026-79239 , GHSA-gq9p-f254-h286

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

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.

Patch / fix

  • maven org.http4s:http4s-ember-core_2.13 0.23.37, 1.0.0-M48
  • maven org.http4s:http4s-ember-core_2.12 0.23.37
  • maven org.http4s:http4s-ember-core_3 0.23.37, 1.0.0-M48
  • typelevel http4s 0.23.37, 1.0.0-M48
  • org.http4s http4s-ember-core_2.12 0.23.37
  • org.http4s http4s-ember-core_2.13 0.23.37, 1.0.0-M48
  • org.http4s http4s-ember-core_3 0.23.37, 1.0.0-M48

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
54 d ago

Exploit prediction

0.63% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
maven org.http4s:http4s-ember-core_2.13
<0.23.37
>=1.0.0-M1, <1.0.0-M48
0.23.37
1.0.0-M48
maven org.http4s:http4s-ember-core_2.12
<0.23.37
0.23.37
maven org.http4s:http4s-ember-core_3
<0.23.37
>=1.0.0-M1, <1.0.0-M48
0.23.37
1.0.0-M48

Affected products

  • http4s http4s

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.