How severe is CVE-2026-69216?

CVE-2026-69216 has a CVSS score of 5.4/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-69216?

CVE-2026-69216 affects the following packages: org.http4s:http4s-ember-core_2.12 (Maven), org.http4s:http4s-ember-core_2.13 (Maven), org.http4s:http4s-ember-core_3 (Maven), org.http4s:http4s-ember-core_2.13 (Maven), org.http4s:http4s-ember-core_3 (Maven). Ecosystems affected: Maven.

How do I fix CVE-2026-69216?

Update org.http4s:http4s-ember-core_2.12 to 0.23.35 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-69216 is resolved across your whole dependency graph.

How do I detect CVE-2026-69216 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4s:http4s-ember-core_2.12, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-69216 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-69216 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-69216 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-69216?

CVE-2026-69216 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 31th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-69216?

CVE-2026-69216 is classified as CWE-444 (CWE-444). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-69216 published, and has it been updated?

CVE-2026-69216 was published on September 15, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

MEDIUM severity

CVE-2026-69216 — http4s-ember-core_2.12

MEDIUMFix: http4s/http4s@d78612a

CVE-2026-69216 is a medium-severity (CVSS 5.4) CWE-444 vulnerability in org.http4s:http4s-ember-core_2.12. A fix is available for org.http4s:http4s-ember-core_2.12 — see the affected versions and patch details below.

Http4s: Ember chunk parser lenience (TE.TE request smuggling)

Also known asGHSA-jrpm-956j-96jg

Published

Sep 15, 2026

Updated

Oct 28, 2026

Affected

5 pkgs

Patched

5 / 5

Exploits

None indexed

Exploitation data as of Oct 29, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-69216.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs31th percentile — riskier than 31% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-69216 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 397,508 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

5 pkgs affected

☕org.http4s:http4s-ember-core_2.12☕org.http4s:http4s-ember-core_2.13☕org.http4s:http4s-ember-core_3☕org.http4s:http4s-ember-core_2.13☕org.http4s:http4s-ember-core_3

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Summary

Ember's chunk decoder parses the size token leniently: it strips leading and trailing whitespace and accepts a leading + or - sign. RFC9112 §7.1 defines chunk-size = 1*HEXDIG. An intermediary that parses the chunk boundary differently (or rejects it) will disagree with Ember on request framing, enabling HTTP request smuggling (TE.TE).

Impact

Server

Request smuggling (TE.TE) when ember-server is an origin behind an intermediary that forwards the body verbatim but interprets the malformed chunk sizes differently

Front-end security bypass: the smuggled request reaches paths the intermediary might have blocked, with attacker-chosen method and headers.
Cache poisoning: the smuggled response is associated with the next request key in a caching proxy.
Request queue hijack:

Client

ember-client has the same leniencies on the response path, which enables response smuggling when http4s is used as a gateway. This is less severe, as it requires a malicious or compromised upstream rather than an anonymous remote client.

Preconditions

Unauthenticated remote attacker (server)
ember-server as origin behind a keep-alive intermediary
Malicious or compromised upstream (client)
Intermediary or upstream forwards chunked bodies without re-encoding and disagrees with Ember on + prefix, - prefix, or leading and trailing octets rather than rejecting.

Workarounds

Intermediary strictly rejects malformed chunk sizes
Intermediary buffers and re-encodes request bodies

References

RFC9112 §7.1: Chunked Transfer Coding

Affected Packages

5 total 5 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.http4s:http4s-ember-core_2.12`	all versions	0.23.35`org.http4s:http4s-ember-core_2.12:0.23.35`
☕Maven	`org.http4s:http4s-ember-core_2.13`	all versions	0.23.35`org.http4s:http4s-ember-core_2.13:0.23.35`
☕Maven	`org.http4s:http4s-ember-core_3`	all versions	0.23.35`org.http4s:http4s-ember-core_3:0.23.35`
☕Maven	`org.http4s:http4s-ember-core_2.13`	≥ 1.0.0-M1&&< 1.0.0-M47	1.0.0-M47`org.http4s:http4s-ember-core_2.13:1.0.0-M47`
☕Maven	`org.http4s:http4s-ember-core_3`	≥ 1.0.0-M1&&< 1.0.0-M47	1.0.0-M47`org.http4s:http4s-ember-core_3:1.0.0-M47`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4s:http4s-ember-core_2.12, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.http4s:http4s-ember-core_2.12 to 0.23.35 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-69216 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

## Summary Ember's chunk decoder parses the size token leniently: it strips leading and trailing whitespace and accepts a leading `+` or `-` sign. RFC9112 §7.1 defines `chunk-size = 1*HEXDIG`. An intermediary that parses the chunk boundary differently (or rejects it) will disagree with Ember on request framing, enabling HTTP request smuggling (TE.TE). ## Impact ### Server Request smuggling (TE.TE) when ember-server is an origin behind an intermediary that forwards the body verbatim but interprets the malformed chunk sizes differently - Front-end security bypass: the smuggled request rea