Vulnerability details
CVE-2026-69218
Http4s Ember HTTP/2: unbounded continuation frame accumulation
Official description
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, When Ember receives an HTTP/2 HEADERS or PUSH_PROMISE frame without END_HEADERS, H2Connection buffers the header block and subsequent CONTINUATION fragments without a size bound. A remote peer can keep an incomplete block open and exhaust heap memory before request decoding, affecting an ember-server or ember-client configured with withHttp2. The remediation tracks accumulated size against SETTINGS_MAX_HEADER_LIST_SIZE derived from EmberServerBuilder.maxHeaderSize or EmberClientBuilder.maxResponseHeaderSize, sends GOAWAY when the limit is exceeded, and applies receiveHeadersTimeout to incomplete blocks. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
CVSS scores
| Score | Version | Source | Vector |
|---|---|---|---|
| 7.5High | 3.1 | CVEProject cvelistV5 (CNA) (GitHub_M) | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Affected products
| Vendor | Product | Versions | Source |
|---|---|---|---|
| http4s | http4s | < 0.23.35 | CVEProject cvelistV5 (CNA) |
| http4s | http4s | >= 1.0.0-M1, < 1.0.0-M47 | CVEProject cvelistV5 (CNA) |
References and advisories
5- https://github.com/http4s/http4s/security/advisories/GHSA-cp4q-fqw9-4hf6 x_refsource_CONFIRM
- https://github.com/http4s/http4s/commit/6e8eccd64a6a74ab4811897881e95e0e1b3a818e x_refsource_MISC
- https://github.com/http4s/http4s/commit/f9dcca4f5a17992ac0972fafd7920f9bc12cdc51 x_refsource_MISC
- https://github.com/http4s/http4s/releases/tag/v0.23.35 x_refsource_MISC
- https://github.com/http4s/http4s/releases/tag/v1.0.0-M47 x_refsource_MISC
Details
- Published
- 2026-09-15
- Last updated
- 2026-09-17
- State
- Published
- Assigner (CNA)
- GitHub_M
Exploit prediction (EPSS)
SSVC assessment (CISA)
- Automatable
- Yes
- Exploitation
- None
- Technical impact
- Partial
Weaknesses (CWE)
- CWE-770Allocation of Resources Without Limits or Throttling