CVE-2026-54556
CVE.org · Published
- Record status
- Published
- Identifier year (not publication year)
- 2026
- Source publication
- Source updated
- Imported by cveboard
- Source snapshot
- cve_2026-10-24_midnight_baseline ·
CNA source text (English)
Http4s: HTTP/2 Denial of Service with Ember Backend
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, an unauthenticated HTTP/2 peer can cause an out-of-memory denial of service in the Ember backend with HTTP/2 enabled. The Hpack wrapper in ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala concatenates HEADERS and CONTINUATION frame fragments and decodes them into a single List, but maxHeaderSize accounting does not include indexed headers or HPACK per-header overhead. A small compressed header block can therefore expand into a much larger decoded representation that remains in memory for processing. Servers exposed to untrusted HTTP/2 traffic and clients directed to an untrusted HTTP/2 server are affected, and concurrent malicious connections can exhaust the process heap. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
Scoped product and version facts
Fix information unknown; no fixed version is derived here. Missing information does not prove that no fix exists.
Exploitation unknown; this catalogue does not assess exploitation.
http4s
- Vendor
- http4s
- Product
- http4s
- Platforms
- Unknown
- Default status
Unknown
| Version (version) | Status (status) | Version scheme (versionType) | Exclusive end (lessThan) | Inclusive end (lessThanOrEqual) | Status changes (at → status) |
|---|---|---|---|---|---|
| < 0.23.35 | affected | Unavailable | Unavailable | Unavailable | None listed |
| >= 1.0.0-M1, < 1.0.0-M46 | affected | Unavailable | Unavailable | Unavailable | None listed |
http4s-ember-core_2.12
- Vendor
- org.http4s
- Product
- http4s-ember-core_2.12
- Platforms
- Unknown
- Default status
Unknown
| Version (version) | Status (status) | Version scheme (versionType) | Exclusive end (lessThan) | Inclusive end (lessThanOrEqual) | Status changes (at → status) |
|---|---|---|---|---|---|
| < 0.23.35 | affected | Unavailable | Unavailable | Unavailable | None listed |
http4s-ember-core_2.13
- Vendor
- org.http4s
- Product
- http4s-ember-core_2.13
- Platforms
- Unknown
- Default status
Unknown
| Version (version) | Status (status) | Version scheme (versionType) | Exclusive end (lessThan) | Inclusive end (lessThanOrEqual) | Status changes (at → status) |
|---|---|---|---|---|---|
| >= 1.0.0-M1, < 1.0.0-M46 | affected | Unavailable | Unavailable | Unavailable | None listed |
| < 0.23.35 | affected | Unavailable | Unavailable | Unavailable | None listed |
http4s-ember-core_3
- Vendor
- org.http4s
- Product
- http4s-ember-core_3
- Platforms
- Unknown
- Default status
Unknown
| Version (version) | Status (status) | Version scheme (versionType) | Exclusive end (lessThan) | Inclusive end (lessThanOrEqual) | Status changes (at → status) |
|---|---|---|---|---|---|
| >= 1.0.0-M1, < 1.0.0-M46 | affected | Unavailable | Unavailable | Unavailable | None listed |
| < 0.23.35 | affected | Unavailable | Unavailable | Unavailable | None listed |