GHSA-cp4q-fqw9-4hf6

Suggest an improvement
Source
https://github.com/advisories/GHSA-cp4q-fqw9-4hf6
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-cp4q-fqw9-4hf6/GHSA-cp4q-fqw9-4hf6.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-cp4q-fqw9-4hf6
Aliases
Published
2026-09-15T20:01:08Z
Modified
2026-09-15T20:15:05Z
Severity
  • 7.5 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
Summary
Http4s Ember HTTP/2: unbounded continuation frame accumulation
Details

When Ember receives an HTTP/2 HEADERS or PUSH_PROMISE frame without the END_HEADERS flag, it buffers the header block fragment and waits for subsequent CONTINUATION frames. These accumulate unbounded until the connection closes.

Impact

A remote, unauthenticated peer can exhaust the heap on any Ember endpoint that has HTTP/2 enabled:

  • ember-server with .withHttp2: any HTTP/2 client can trigger this against any reachable path (including paths that return 404). No authentication is required because the attack completes before the request is decoded.
  • ember-client with .withHttp2: a malicious or compromised origin server can trigger this via the response header block. A single in-flight request is sufficient.

Memory consumption is bounded only by the attacker's upload bandwidth and the connection lifetime.

Prerequisites

  • EmberServerBuilder configured with .withHttp2.
    • For the server: the attacker can establish an HTTP/2 connection
    • For the client: the application makes a request to an attacker-controlled origin. HTTP/2 incoming headers exceeding the configured size limit are buffer in order to generate an informative HTTP 413 response. If a client does not stop sending headers, this leads to memory exhaustion.

Patches

The fix bounds the accumulated header-block size at SETTINGS_MAX_HEADER_LIST_SIZE (derived from EmberServerBuilder.maxHeaderSize / EmberClientBuilder.maxResponseHeaderSize). When a CONTINUATION frame would push the accumulated block over that limit, the connection is terminated with GOAWAY. The receiveHeadersTimeout additionally bounds how long an incomplete header block may remain open.

Workarounds

  • Disable HTTP/2 (.withHttp2) until upgraded (default). It is off by default.
  • If HTTP/2 must remain enabled, place ember behind a reverse proxy that terminates HTTP/2 and speaks HTTP/1.1 to ember.
Database specific 
{
    "cwe_ids":  [
        "CWE-770"
    ],
    "github_reviewed":  true,
    "github_reviewed_at":  "2026-09-15T20:01:08Z",
    "nvd_published_at":  null,
    "severity":  "HIGH"
}
References

Affected packages

Maven
org.http4s:http4s-ember-core_2.12

Package

Name
org.http4s:http4s-ember-core_2.12
View open source insights on deps.dev
Purl
pkg:maven/org.http4s/http4s-ember-core_2.12

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
0.23.35

Affected versions

0.*
0.10.0-M10
0.21.0-M2
0.21.0-M3
0.21.0-M4
0.21.0-M5
0.21.0-M6
0.21.0-RC1
0.21.0-RC2
0.21.0-RC3
0.21.0-RC4
0.21.0-RC5
0.21.0
0.21.1
0.21.2
0.21.3
0.21.4
0.21.5
0.21.6
0.21.7
0.21.8
0.21.9
0.21.11
0.21.12
0.21.13
0.21.14
0.21.15
0.21.16
0.21.17
0.21.18
0.21.19
0.21.20
0.21.21
0.21.22
0.21.23
0.21.24
0.21.25
0.21.26
0.21.27
0.21.28
0.21.29
0.21.30
0.21.31
0.21.32
0.21.33
0.21.34
0.22.0-M1
0.22.0-M2
0.22.0-M3
0.22.0-M4
0.22.0-M5
0.22.0-M6
0.22.0-M7
0.22.0-M8
0.22.0-RC1
0.22.0
0.22-53-01128f5
0.22-96-55d3184
0.22-129-24d065b
0.22-143-49b5a8d
0.22.1
0.22.2
0.22.3
0.22.4
0.22.5
0.22.6
0.22.7
0.22.8
0.22.9
0.22.10
0.22.11
0.22.12
0.22.13
0.22.14
0.22.15
0.23.0-M1
0.23.0-RC1
0.23.0
0.23.1
0.23.2
0.23.3
0.23.4
0.23.5
0.23.6
0.23.7
0.23.8
0.23.9
0.23.10
0.23.11
0.23.12
0.23.13
0.23.14
0.23.15
0.23.16
0.23.17
0.23.18
0.23.19-RC1
0.23.19-RC2
0.23.19-RC3
0.23.19
0.23.20
0.23.21
0.23.22
0.23.23
0.23.24
0.23.25
0.23.26
0.23.27
0.23.28
0.23.29
0.23.30
0.23.31
0.23.32
0.23.33
0.23.34

Database specific

last_known_affected_version_range 
"<= 0.23.34"
source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-cp4q-fqw9-4hf6/GHSA-cp4q-fqw9-4hf6.json"
org.http4s:http4s-ember-core_2.13

Package

Name
org.http4s:http4s-ember-core_2.13
View open source insights on deps.dev
Purl
pkg:maven/org.http4s/http4s-ember-core_2.13

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
0.23.35

Affected versions

0.*
0.10.0-M10
0.21.0-M2
0.21.0-M3
0.21.0-M4
0.21.0-M5
0.21.0-M6
0.21.0-RC1
0.21.0-RC2
0.21.0-RC3
0.21.0-RC4
0.21.0-RC5
0.21.0
0.21.1
0.21.2
0.21.3
0.21.4
0.21.5
0.21.6
0.21.7
0.21.8
0.21.9
0.21.11
0.21.12
0.21.13
0.21.14
0.21.15
0.21.16
0.21.17
0.21.18
0.21.19
0.21.20
0.21.21
0.21.22
0.21.23
0.21.24
0.21.25
0.21.26
0.21.27
0.21.28
0.21.29
0.21.30
0.21.31
0.21.32
0.21.33
0.21.34
0.22.0-M1
0.22.0-M2
0.22.0-M3
0.22.0-M4
0.22.0-M5
0.22.0-M6
0.22.0-M7
0.22.0-M8
0.22.0-RC1
0.22.0
0.22-53-01128f5
0.22-96-55d3184
0.22-129-24d065b
0.22-143-49b5a8d
0.22.1
0.22.2
0.22.3
0.22.4
0.22.5
0.22.6
0.22.7
0.22.8
0.22.9
0.22.10
0.22.11
0.22.12
0.22.13
0.22.14
0.22.15
0.23.0-M1
0.23.0-RC1
0.23.0
0.23.1
0.23.2
0.23.3
0.23.4
0.23.5
0.23.6
0.23.7
0.23.8
0.23.9
0.23.10
0.23.11
0.23.12
0.23.13
0.23.14
0.23.15
0.23.16
0.23.17
0.23.18
0.23.19-RC1
0.23.19-RC2
0.23.19-RC3
0.23.19
0.23.20
0.23.21
0.23.22
0.23.23
0.23.24
0.23.25
0.23.26
0.23.27
0.23.28
0.23.29
0.23.30
0.23.31
0.23.32
0.23.33
0.23.34

Database specific

last_known_affected_version_range 
"<= 0.23.34"
source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-cp4q-fqw9-4hf6/GHSA-cp4q-fqw9-4hf6.json"
org.http4s:http4s-ember-core_3

Package

Name
org.http4s:http4s-ember-core_3
View open source insights on deps.dev
Purl
pkg:maven/org.http4s/http4s-ember-core_3

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
0.23.35

Affected versions

0.*
0.22.0-M8
0.22.0-RC1
0.22.0
0.22.1
0.22.2
0.22.3
0.22.4
0.22.5
0.22.6
0.22.7
0.22.8
0.22.9
0.22.10
0.22.11
0.22.12
0.22.13
0.22.14
0.22.15
0.23.0-M1
0.23.0-RC1
0.23.0
0.23.1
0.23.2
0.23.3
0.23.4
0.23.5
0.23.6
0.23.7
0.23.8
0.23.9
0.23.10
0.23.11
0.23.12
0.23.13
0.23.14
0.23.15
0.23.16
0.23.17
0.23.18
0.23.19-RC1
0.23.19-RC2
0.23.19-RC3
0.23.19
0.23.20
0.23.21
0.23.22
0.23.23
0.23.24
0.23.25
0.23.26
0.23.27
0.23.28
0.23.29
0.23.30
0.23.31
0.23.32
0.23.33
0.23.34

Database specific

last_known_affected_version_range 
"<= 0.23.34"
source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-cp4q-fqw9-4hf6/GHSA-cp4q-fqw9-4hf6.json"
org.http4s:http4s-ember-core_2.13

Package

Name
org.http4s:http4s-ember-core_2.13
View open source insights on deps.dev
Purl
pkg:maven/org.http4s/http4s-ember-core_2.13

Affected ranges

Type
ECOSYSTEM
Events
Introduced
1.0.0-M1
Fixed
1.0.0-M47

Affected versions

1.*
1.0.0-M2
1.0.0-M3
1.0.0-M4
1.0.0-M5
1.0.0-M6
1.0.0-M7
1.0.0-M8
1.0.0-M9
1.0.0-M10
1.0.0-M11
1.0.0-M13
1.0.0-M14
1.0.0-M15
1.0.0-M16
1.0.0-M17
1.0.0-M18
1.0.0-M19
1.0.0-M20
1.0.0-M21
1.0.0-M22
1.0.0-M23
1.0.0-M24
1.0.0-M25
1.0.0-M27
1.0.0-M28
1.0.0-M29
1.0.0-M30
1.0.0-M31
1.0.0-M32
1.0.0-M33
1.0.0-M34
1.0.0-M35
1.0.0-M36
1.0.0-M37
1.0.0-M38
1.0.0-M39
1.0.0-M40
1.0.0-M41
1.0.0-M42
1.0.0-M43
1.0.0-M44
1.0.0-M45
1.0.0-M46

Database specific

last_known_affected_version_range 
"<= 1.0.0-M46"
source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-cp4q-fqw9-4hf6/GHSA-cp4q-fqw9-4hf6.json"
org.http4s:http4s-ember-core_3

Package

Name
org.http4s:http4s-ember-core_3
View open source insights on deps.dev
Purl
pkg:maven/org.http4s/http4s-ember-core_3

Affected ranges

Type
ECOSYSTEM
Events
Introduced
1.0.0-M1
Fixed
1.0.0-M47

Affected versions

1.*
1.0.0-M22
1.0.0-M23
1.0.0-M24
1.0.0-M25
1.0.0-M27
1.0.0-M28
1.0.0-M29
1.0.0-M30
1.0.0-M31
1.0.0-M32
1.0.0-M33
1.0.0-M34
1.0.0-M35
1.0.0-M36
1.0.0-M37
1.0.0-M38
1.0.0-M39
1.0.0-M40
1.0.0-M41
1.0.0-M42
1.0.0-M43
1.0.0-M44
1.0.0-M45
1.0.0-M46

Database specific

last_known_affected_version_range 
"<= 1.0.0-M46"
source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-cp4q-fqw9-4hf6/GHSA-cp4q-fqw9-4hf6.json"