CVE-2026-69202· NVD / CVE Program· CNA GitHub_M

Http4s Ember HTTP/2: unbounded inbound body buffering

Noroxi assessment

Priority: Monitor (action score 30/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.63% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: org.http4s:http4s-ember-core_2.12 (Maven) 0.23.35; org.http4s:http4s-ember-core_2.13 (Maven) 1.0.0-M47, 0.23.35; org.http4s:http4s-ember-core_3 (Maven) 1.0.0-M47, 0.23.35.

Low priority for now. Upgrade to org.http4s:http4s-ember-core_2.12 (Maven) 0.23.35; org.http4s:http4s-ember-core_2.13 (Maven) 1.0.0-M47, 0.23.35; org.http4s:http4s-ember-core_3 (Maven) 1.0.0-M47, 0.23.35 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HTTP/2 flow-control window is replenished according to bytes received from the network rather than bytes consumed by the application, while each stream stores DATA in an unbounded channel. A hostile peer can therefore send a body faster than a slow or non-draining application consumes it, retaining payloads in heap on an ember-server or ember-client configured with withHttp2. The patch bounds the per-stream H2Connection body channel so application consumption applies backpressure. This issue is fixed in versions 0.23.35 and 1.0.0-M47.

HighCVSS 7.5 · v3.1—No exploit Fix available

Published: Sep 15, 2026
Updated: Sep 16, 2026
EPSS: 0.6% · 49th percentile
CWE: CWE-400

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.6%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · GitHub_M: 7.5; NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

http4s http4s
- < 0.23.35, >= 1.0.0-M1, < 1.0.0-M47affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Maven	org.http4s:http4s-ember-core_2.12	before 0.23.35	0.23.35
Maven	org.http4s:http4s-ember-core_2.13	from 1.0.0-M1 · before 1.0.0-M47	1.0.0-M47
Maven	org.http4s:http4s-ember-core_2.13	before 0.23.35	0.23.35
Maven	org.http4s:http4s-ember-core_3	from 1.0.0-M1 · before 1.0.0-M47	1.0.0-M47
Maven	org.http4s:http4s-ember-core_3	before 0.23.35	0.23.35

Same product

http4s: all records

Other highest-scoring records for the same primary product.

CVE-2026-69204Http4s: Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)
36Monitor
CVE-2026-69217Http4s: Ember Server accepts duplicate Content-Length headers
34Monitor
CVE-2026-69205Http4s: Ember Transfer-Encoding value parsing (TE.CL / TE.0 request smuggling)
34Monitor

Published before and after this one in the same product

← EarlierCVE-2026-69214Sep 15, 2026 · Http4s: CookieJar middleware accepts arbitrary Set-Cookie domain
27Monitor
← EarlierCVE-2026-69216Sep 15, 2026 · Http4s: Ember chunk parser lenience (TE.TE request smuggling)
21Monitor
Later →CVE-2026-69203Sep 15, 2026 · Http4s Ember HTTP/2: does not enforce SETTINGS_MAX_CONCURRENT_STREAMS
30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Maven:org.http4s:http4s-ember-core_2.12	0.23.35	Package registry (OSV)
Maven:org.http4s:http4s-ember-core_2.13	0.23.35	Package registry (OSV)
Maven:org.http4s:http4s-ember-core_2.13	1.0.0-M47	Package registry (OSV)
Maven:org.http4s:http4s-ember-core_3	0.23.35	Package registry (OSV)
Maven:org.http4s:http4s-ember-core_3	1.0.0-M47	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

http4s/http4scommit 22d2335

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-692030 days apartHttp4s Ember HTTP/2: does not enforce SETTINGS_MAX_CONCURRENT_STREAMS
30Monitor
CVE-2026-692080 days apartHttp4s: DigestAuth nonce map grows unbounded
30Monitor
CVE-2026-692090 days apartHttp4s: WebSocket decoder accepts unbounded message sizes
30Monitor
CVE-2026-692130 days apartHttp4s Ember HTTP/2: unbounded outbound frame queue
30Monitor
CVE-2026-889750 days apartHttp4s: Ember HTTP/2 buffers a frame's declared payload before checking SETTINGS_MAX_FRAME_SIZE
30Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: none
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-secondary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log

Fix✗ → ✓Sep 28, 2026, 10:45 PM UTC

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References

github.com/http4s/http4s/commit/22d2335975d02dc9fb9fb75cfe002279521d86ac

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records