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CVE-2026-78669· CVE.org (no NVD analysis yet)· CNA Go

Excessive CPU consumption from repeated initial window changes in net/http

A malicious HTTP/2 peer can cause excessive CPU consumption in the client or server by opening a large number of streams and then sending many small SETTINGS frames containing SETTINGS_INITIAL_WINDOW_SIZE values.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Oct 8, 2026
Updated
Oct 9, 2026
EPSS
0.6% · 45th percentile
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Report tools

JSON

Action score

30

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.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

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Affected systems

—

Versions reported by the vendor

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

  • Go standard library net/http

    • before 1.26.9affected · semver

  • Go standard library net/http/internal/http2

    • 1.27.0-0 and later · before 1.27.2affected · semver

  • golang.org/x/net golang.org/x/net/http2

    • before 0.60.0affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12golang-1.19all versions—
Debian:12golang-golang-x-netall versions—
Debian:13golang-1.24all versions—
Debian:14golang-1.25all versions—
Debian:14golang-1.26all versions—
Debian:14golang-1.27all versions—
Gogolang.org/x/netbefore 0.60.00.60.0
Gostdlibfrom 1.27.0-0 · before 1.27.21.27.2
Gostdlibbefore 1.26.91.26.9

Same product

go standard library: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-45288HTTP/2 CONTINUATION flood in net/http
    58Plan
  • CVE-2026-78663Double flow control refund on HTTP/2 server streams in net/http
    36Monitor
  • CVE-2026-94439HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http
    30Monitor
  • CVE-2026-78667Lack of limit on size of parsed Range headers in net/http
    30Monitor
  • CVE-2026-78660HTTP/2 transport accepts malformed framing-related headers in net/http
    30Monitor
  • CVE-2026-78659HTTP/2 server memory exhaustion due to Trailer headers in net/http
    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 / packageFixed versionSource
Go standard library net/http1.26.9Vendor (CNA)
Go standard library net/http/internal/http21.27.2Vendor (CNA)
golang.org/x/net golang.org/x/net/http20.60.0Vendor (CNA)
Go:golang.org/x/net0.60.0Package registry (OSV)
Go:stdlib1.26.9Package registry (OSV)
Go:stdlib1.27.2Package 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.

  1. Published
  2. Fix recordedsame day
  3. TodayOct 11, 2026+3 d
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.

No commit or PR link among the references.

Credits

All researchers

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

Variant candidates

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

  • CVE-2026-786590 days apartHTTP/2 server memory exhaustion due to Trailer headers in net/http
    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-405 · Asymmetric Resource Consumption (Amplification)

CVSS vector

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

nvd-secondary

Attack context

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

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. CVSS— → 7.5
  2. Severity— → high
  3. SSVC exploitation— → none
  4. Exploit maturity— → none
  5. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

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

All records