GHSA-8F3Q-3JMV-7PRW
Vulnerability from github – Published: 2026-09-15 20:00 – Updated: 2026-09-15 20:00
VLAI
Summary
Http4s Ember HTTP/2 has an unbounded outbound frame queue
Details
Ember's HTTP/2 connection serializes all outgoing frames through a single unbounded queue drained by one writer fiber (writeLoop). When the write side stalls, any frames the connection keeps producing accumulate in that queue without limit. The peer can drive this cheaply because the connection emits a control frame in response to inbound frames it does not flow-control: one PING ACK per PING, one SETTINGS ACK per SETTINGS, and a WINDOW_UPDATE per inbound DATA. A single unauthenticated connection can therefore exhaust heap and OOM the process.
This affects an ember server (malicious client) and an ember client (malicious/compromised server that floods the client and stops reading its ACKs).
Impact
Unauthenticated remote denial of service (OOM) against any ember server built .withHttp2, from a single connection, at negligible attacker cost (tiny control frames). Also affects an ember client talking to a hostile HTTP/2 server.
Preconditions
- Ember server or client built
.withHttp2, speaking to a hostile or compromised peer.
Workarounds
- Disable HTTP/2 (do not call
.withHttp2).
Severity
7.5 (High)
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.23.34"
},
"package": {
"ecosystem": "Maven",
"name": "org.http4s:http4s-ember-core_2.12"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.23.35"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.23.34"
},
"package": {
"ecosystem": "Maven",
"name": "org.http4s:http4s-ember-core_2.13"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.23.35"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.23.34"
},
"package": {
"ecosystem": "Maven",
"name": "org.http4s:http4s-ember-core_3"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.23.35"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 1.0.0-M46"
},
"package": {
"ecosystem": "Maven",
"name": "org.http4s:http4s-ember-core_3"
},
"ranges": [
{
"events": [
{
"introduced": "1.0.0-M1"
},
{
"fixed": "1.0.0-M47"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 1.0.0-M46"
},
"package": {
"ecosystem": "Maven",
"name": "org.http4s:http4s-ember-core_2.13"
},
"ranges": [
{
"events": [
{
"introduced": "1.0.0-M1"
},
{
"fixed": "1.0.0-M47"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-69213"
],
"database_specific": {
"cwe_ids": [
"CWE-400",
"CWE-770"
],
"github_reviewed": true,
"github_reviewed_at": "2026-09-15T20:00:36Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "Ember\u0027s HTTP/2 connection serializes all outgoing frames through a single unbounded queue drained by one writer fiber (`writeLoop`). When the write side stalls, any frames the connection keeps producing accumulate in that queue without limit. The peer can drive this cheaply because the connection emits a control frame in response to inbound frames it does not flow-control: one `PING` ACK per `PING`, one `SETTINGS` ACK per `SETTINGS`, and a `WINDOW_UPDATE` per inbound DATA. A single unauthenticated connection can therefore exhaust heap and OOM the process.\n\nThis affects an ember server (malicious client) and an ember client (malicious/compromised server that floods the client and stops reading its ACKs).\n\n## Impact\n\nUnauthenticated remote denial of service (OOM) against any ember server built `.withHttp2`, from a single connection, at negligible attacker cost (tiny control frames). Also affects an ember client talking to a hostile HTTP/2 server.\n\n## Preconditions\n\n- Ember server or client built `.withHttp2`, speaking to a hostile or compromised peer.\n\n## Workarounds\n\n- Disable HTTP/2 (do not call `.withHttp2`).",
"id": "GHSA-8f3q-3jmv-7prw",
"modified": "2026-09-15T20:00:36Z",
"published": "2026-09-15T20:00:36Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/http4s/http4s/security/advisories/GHSA-8f3q-3jmv-7prw"
},
{
"type": "WEB",
"url": "https://github.com/http4s/http4s/commit/13fe24d6440bde2f1eb70121486cf59c278e6bae"
},
{
"type": "PACKAGE",
"url": "https://github.com/http4s/http4s"
},
{
"type": "WEB",
"url": "https://github.com/http4s/http4s/releases/tag/v0.23.35"
},
{
"type": "WEB",
"url": "https://github.com/http4s/http4s/releases/tag/v1.0.0-M47"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
],
"summary": "Http4s Ember HTTP/2 has an unbounded outbound frame queue"
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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