Double flow control refund on HTTP/2 server streams in net/http
Priority MEDIUM 49CWE-675Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · High · High
- Fix status
- Partial Red Hat: 18 fixed, 28 without a fix
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and Red Hat.
Summary
The Go standard library net/http before 1.26.9, net/http/internal/http2 from 1.27.0-0 before 1.27.2, and golang.org/x/net/http2 before 0.60.0 are affected. The HTTP/2 server refunds connection-level flow control twice for the same data, once when a client resets a stream and again when a handler reads the buffered data (CWE-675). A remote, unauthenticated client can bypass the configured MaxReceiveBufferPerConnection limit, which leads to high integrity and availability impact.
Written with Claude Haiku 5.5 from the sources below · 2026-10-31
Description from the CNA
The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client can exploit this to bypass the configured connection-level flow control limit (MaxReceiveBufferPerConnection). Total buffered data is still limited by the concurrent stream limit and stream-level flow control.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00858 58th percentileScored 2026-11-07
Fix Partial net/http (Go standard library): 1.26.9net/http/internal/http2 (Go standard library): 1.27.2+1 more productRed Hat: 15 advisoriesRed Hat: 18 fixed, 28 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Go standard library | net/http | before 1.26.9 | 1.26.9 | Patch available | CNA |
| Go standard library | net/http/internal/http2 | 1.27.0-0 to before 1.27.2 | 1.27.2 | Patch available | CNA |
| Go standard library | golang.org/x/net/http2 | before 0.60.0 | 0.60.0 | Patch available | CNA |
- net/http VendorGo standard library Affected before 1.26.9 Fixed in 1.26.9 Patch available CNA
- net/http/internal/http2 VendorGo standard library Affected 1.27.0-0 to before 1.27.2 Fixed in 1.27.2 Patch available CNA
- golang.org/x/net/http2 VendorGo standard library Affected before 0.60.0 Fixed in 0.60.0 Patch available CNA
CPE names Threatist (inferred) · 1
Inferred from how NVD named this product before; not given by a source.
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:golang:go:*:*:*:*:*:*:*:* | — | — | Go standard library |
- cpe:2.3:a:golang:go:*:*:*:*:*:*:*:* Versions — — ·Go standard library
Remediation
Upgrade Go net/http to 1.26.9, net/http/internal/http2 to 1.27.2, or golang.org/x/net/http2 to 0.60.0. Red Hat fixes it in RHSA-2026:92516, RHSA-2026:92509, RHSA-2026:92497, RHSA-2026:92480, RHSA-2026:92451, RHSA-2026:90994, RHSA-2026:87245, RHSA-2026:87246, RHSA-2026:87043, RHSA-2026:87042, RHSA-2026:87041, RHSA-2026:87040, RHSA-2026:86196, RHSA-2026:86203 and RHSA-2026:86093. The sources list no fixed version for OpenShift Pipelines, OpenShift Serverless and other products.
Written with Claude Haiku 5.5 from the sources below · 2026-10-31
- Fix · CNA net/http (Go standard library) Fixed in 1.26.9
- Fix · CNA net/http/internal/http2 (Go standard library) Fixed in 1.27.2
- Fix · CNA golang.org/x/net/http2 (golang.org/x/net) Fixed in 0.60.0
Red Hat 15 advisories
- RHSA-2026:92516 Released 2026-10-29 · Red Hat rating ImportantRed Hat OpenShift Service Mesh 3.4.4
- Red Hat OpenShift Service Mesh 3.4 registry.redhat.io/openshift-service-mesh/istio-cni-rhel9, registry.redhat.io/openshift-service-mesh/istio-pilot-rhel9, registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9 +1
- RHSA-2026:92509 Released 2026-10-29 · Red Hat rating ImportantRed Hat OpenShift Service Mesh 3.3.9
- Red Hat OpenShift Service Mesh 3.3 registry.redhat.io/openshift-service-mesh/istio-cni-rhel9, registry.redhat.io/openshift-service-mesh/istio-pilot-rhel9, registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9 +1
- RHSA-2026:92497 Released 2026-10-29 · Red Hat rating ImportantRed Hat OpenShift Service Mesh 3.2.11
- Red Hat OpenShift Service Mesh 3.2 registry.redhat.io/openshift-service-mesh/istio-cni-rhel9, registry.redhat.io/openshift-service-mesh/istio-pilot-rhel9, registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9 +1
Show 12 more Red Hat advisories
- RHSA-2026:92480 Released 2026-10-29 · Red Hat rating ImportantRed Hat OpenShift Service Mesh 3.1.14
- Red Hat OpenShift Service Mesh 3.1 registry.redhat.io/openshift-service-mesh/istio-cni-rhel9, registry.redhat.io/openshift-service-mesh/istio-pilot-rhel9, registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9 +1
- RHSA-2026:92451 Released 2026-10-29 · Red Hat rating ImportantRed Hat OpenShift Service Mesh 3.0.17
- Red Hat OpenShift Service Mesh 3.0 registry.redhat.io/openshift-service-mesh/istio-cni-rhel9, registry.redhat.io/openshift-service-mesh/istio-pilot-rhel9, registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9 +1
- RHSA-2026:90994 Released 2026-10-27 · Red Hat rating Importantgo-toolset:rhel8 security, bug fix, and enhancement update
- Red Hat Enterprise Linux AppStream AUS (v.8.4) delve-1.26.1-1.module+el8.4.0+25181+7ce5b91c.src::go-toolset:rhel8, delve-1.26.1-1.module+el8.4.0+25181+7ce5b91c.x86_64::go-toolset:rhel8, go-toolset-1.26.10-2.module+el8.4.0+25201+9a419e96.x86_64::go-toolset:rhel8 +8
- Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) delve-1.26.1-1.module+el8.4.0+25181+7ce5b91c.src::go-toolset:rhel8, delve-1.26.1-1.module+el8.4.0+25181+7ce5b91c.x86_64::go-toolset:rhel8, go-toolset-1.26.10-2.module+el8.4.0+25201+9a419e96.x86_64::go-toolset:rhel8 +8
- RHSA-2026:87245 Released 2026-10-21 · Red Hat rating Importantgo-toolset:rhel8 security, bug fix, and enhancement update
- Red Hat Enterprise Linux AppStream E4S (v.8.8) delve-1.26.1-1.module+el8.8.0+24781+86ad105d.ppc64le::go-toolset:rhel8, delve-1.26.1-1.module+el8.8.0+24781+86ad105d.src::go-toolset:rhel8, delve-1.26.1-1.module+el8.8.0+24781+86ad105d.x86_64::go-toolset:rhel8 +13
- Red Hat Enterprise Linux AppStream TUS (v.8.8) delve-1.26.1-1.module+el8.8.0+24781+86ad105d.src::go-toolset:rhel8, delve-1.26.1-1.module+el8.8.0+24781+86ad105d.x86_64::go-toolset:rhel8, go-toolset-1.26.10-4.module+el8.8.0+25113+a148ecc0.x86_64::go-toolset:rhel8 +8
- RHSA-2026:87246 Released 2026-10-21 · Red Hat rating Importantgo-toolset:rhel8 security, bug fix, and enhancement update
- Red Hat Enterprise Linux AppStream AUS (v.8.6) delve-1.26.1-1.module+el8.6.0+24782+a062e766.src::go-toolset:rhel8, delve-1.26.1-1.module+el8.6.0+24782+a062e766.x86_64::go-toolset:rhel8, go-toolset-1.26.10-4.module+el8.6.0+25114+90ecdb41.x86_64::go-toolset:rhel8 +8
- Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) delve-1.26.1-1.module+el8.6.0+24782+a062e766.src::go-toolset:rhel8, delve-1.26.1-1.module+el8.6.0+24782+a062e766.x86_64::go-toolset:rhel8, go-toolset-1.26.10-4.module+el8.6.0+25114+90ecdb41.x86_64::go-toolset:rhel8 +8
- RHSA-2026:87043 Released 2026-10-21 · Red Hat rating Importantgolang security, bug fix, and enhancement update
- Red Hat Enterprise Linux AppStream EUS (v.9.6) go-toolset-1.26.10-1.el9_6, golang-1.26.10-1.el9_6, golang-bin-1.26.10-1.el9_6 +5
- RHSA-2026:87042 Released 2026-10-21 · Red Hat rating Importantgolang security, bug fix, and enhancement update
- Red Hat Enterprise Linux AppStream E4S (v.9.4) go-toolset-1.26.10-1.el9_4, golang-1.26.10-1.el9_4, golang-bin-1.26.10-1.el9_4 +5
- RHSA-2026:87041 Released 2026-10-21 · Red Hat rating Importantgolang security, bug fix, and enhancement update
- Red Hat Enterprise Linux AppStream E4S (v.9.2) go-toolset-1.26.10-1.el9_2, golang-1.26.10-1.el9_2, golang-bin-1.26.10-1.el9_2 +5
- RHSA-2026:87040 Released 2026-10-21 · Red Hat rating Importantgolang security, bug fix, and enhancement update
- Red Hat Enterprise Linux AppStream EUS (v. 10.0) go-toolset-1.26.10-1.el10_0, golang-1.26.10-1.el10_0, golang-bin-1.26.10-1.el10_0 +5
- RHSA-2026:86196 Released 2026-10-20 · Red Hat rating Importantgolang security, bug fix, and enhancement update
- Red Hat Enterprise Linux AppStream (v. 9) go-toolset-1.26.10-1.el9_8, golang-1.26.10-1.el9_8, golang-bin-1.26.10-1.el9_8 +5
- RHSA-2026:86203 Released 2026-10-20 · Red Hat rating Importantgo-toolset:rhel8 security, bug fix, and enhancement update
- Red Hat Enterprise Linux AppStream (v. 8) delve-1.26.1-1.module+el8.10.0+24516+40554724.aarch64::go-toolset:rhel8, delve-1.26.1-1.module+el8.10.0+24516+40554724.ppc64le::go-toolset:rhel8, delve-1.26.1-1.module+el8.10.0+24516+40554724.src::go-toolset:rhel8 +22
- RHSA-2026:86093 Released 2026-10-20 · Red Hat rating Importantgolang security, bug fix, and enhancement update
- Red Hat Enterprise Linux AppStream (v. 10) go-toolset-1.26.10-1.el10_2, golang-1.26.10-1.el10_2, golang-bin-1.26.10-1.el10_2 +5
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Release ·
golang.org/x/net/http2 0.60.0
5 records Highest priority Priority MEDIUM 5 MEDIUM
Other records, highest priority first
- TI-2026-69841 Race condition in Go net/http HPACK encoder crashes HTTP/2 serversPriority MEDIUM 40
- TI-2026-69828 Excessive CPU use from repeated window changes in Go net/httpPriority MEDIUM 40
- TI-2026-69825 Go net/http HTTP/2 transport accepts malformed framing headersPriority MEDIUM 40
- Release ·
Go standard library net/http, net/http/internal/http2 1.26.9, 1.27.2
5 records Highest priority Priority MEDIUM 5 MEDIUM
Other records, highest priority first
- TI-2026-69841 Race condition in Go net/http HPACK encoder crashes HTTP/2 serversPriority MEDIUM 40
- TI-2026-69828 Excessive CPU use from repeated window changes in Go net/httpPriority MEDIUM 40
- TI-2026-69825 Go net/http HTTP/2 transport accepts malformed framing headersPriority MEDIUM 40
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| OpenShift Developer Tools and Services | Affected | No fix planned: Out of support scope |
| OpenShift Pipelines | Affected | No fix yet: Fix deferred |
| OpenShift Serverless | Affected | No fix yet: Fix deferred |
| OpenShift Service Mesh 3 | Affected | No fix yet |
| Red Hat Ansible Automation Platform 2 | Affected | No fix yet: Fix deferred |
| Red Hat Ceph Storage 7 | Affected | No fix yet: Fix deferred |
| Red Hat Ceph Storage 8 | Affected | No fix yet: Fix deferred |
| Red Hat Ceph Storage 9 | Affected | No fix yet: Fix deferred |
| Red Hat Certification Program for Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat Edge Manager 1 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 7 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux AI (RHEL AI) 3 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift AI (RHOAI) | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet |
| Red Hat OpenShift Container Platform 5 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Virtualization 4 | Affected | No fix yet |
| Red Hat OpenShift on AWS | Affected | No fix yet: Fix deferred |
| Red Hat OpenStack Platform 16.2 | Affected | No fix planned: Out of support scope |
| Red Hat OpenStack Platform 17.1 | Affected | No fix planned: Out of support scope |
| Red Hat OpenStack Platform 18.0 | Affected | No fix yet: Fix deferred |
| Red Hat Satellite 6 | Affected | No fix yet: Fix deferred |
| Red Hat Service Interconnect 1 | Affected | No fix planned: Out of support scope |
| Red Hat Service Interconnect 2 | Affected | No fix yet: Fix deferred |
| streams for Apache Kafka 2 | Affected | No fix planned: Out of support scope |
| streams for Apache Kafka 3 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux AppStream (v. 10) | Fixed | RHSA-2026:86093 |
| Red Hat Enterprise Linux AppStream (v. 8) | Fixed | RHSA-2026:86203 |
| Red Hat Enterprise Linux AppStream (v. 9) | Fixed | RHSA-2026:86196 |
| Red Hat Enterprise Linux AppStream AUS (v.8.4) | Fixed | RHSA-2026:90994 |
| Red Hat Enterprise Linux AppStream AUS (v.8.6) | Fixed | RHSA-2026:87246 |
| Red Hat Enterprise Linux AppStream E4S (v.8.8) | Fixed | RHSA-2026:87245 |
| Red Hat Enterprise Linux AppStream E4S (v.9.2) | Fixed | RHSA-2026:87041 |
| Red Hat Enterprise Linux AppStream E4S (v.9.4) | Fixed | RHSA-2026:87042 |
| Red Hat Enterprise Linux AppStream EUS (v. 10.0) | Fixed | RHSA-2026:87040 |
| Red Hat Enterprise Linux AppStream EUS (v.9.6) | Fixed | RHSA-2026:87043 |
| Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) | Fixed | RHSA-2026:90994 |
| Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) | Fixed | RHSA-2026:87246 |
| Red Hat Enterprise Linux AppStream TUS (v.8.8) | Fixed | RHSA-2026:87245 |
| Red Hat OpenShift Service Mesh 3.0 | Fixed | RHSA-2026:92451 |
| Red Hat OpenShift Service Mesh 3.1 | Fixed | RHSA-2026:92480 |
| Red Hat OpenShift Service Mesh 3.2 | Fixed | RHSA-2026:92497 |
| Red Hat OpenShift Service Mesh 3.3 | Fixed | RHSA-2026:92509 |
| Red Hat OpenShift Service Mesh 3.4 | Fixed | RHSA-2026:92516 |
Not affected: 5 products
- Red Hat OpenShift Service Mesh 3.0
- Red Hat OpenShift Service Mesh 3.1
- Red Hat OpenShift Service Mesh 3.2
- Red Hat OpenShift Service Mesh 3.3
- Red Hat OpenShift Service Mesh 3.4
Timeline
- 2026-10-09 Threatist record created from CVE-2026-78663
- 2026-10-10 CVSS score added · CISA ADP
- 2026-10-10 Weakness changed · CISA ADP
- 2026-10-10 CISA SSVC decision points changed
- 2026-10-10 Priority changed: LOW → MEDIUM
- 2026-10-23 Fix available: RHSA-2026:87246 · Red Hat
- 2026-10-23 Fix available: RHSA-2026:86093 · Red Hat
- 2026-10-23 Fix available: RHSA-2026:86196 · Red Hat
- 2026-10-23 Fix available: RHSA-2026:86203 · Red Hat
- 2026-10-23 Fix available: RHSA-2026:87042 · Red Hat
- 2026-10-23 Fix available: RHSA-2026:87040 · Red Hat
- 2026-10-23 Fix available: RHSA-2026:87041 · Red Hat
- 2026-10-23 Fix available: RHSA-2026:87043 · Red Hat
- 2026-10-23 Fix available: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux AppStream (v. 8), Red Hat Enterprise Linux AppStream (v. 9) +6 · Red Hat
- 2026-10-24 Fix available: RHSA-2026:87245 · Red Hat
- 2026-10-24 Fix available: Red Hat Enterprise Linux AppStream E4S (v.8.8), Red Hat Enterprise Linux AppStream TUS (v.8.8) · Red Hat
- 2026-10-29 Fix available: RHSA-2026:90994 · Red Hat
- 2026-10-29 Fix available: Red Hat Enterprise Linux AppStream AUS (v.8.4), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) · Red Hat
- 2026-10-30 Fix available: RHSA-2026:92451 · Red Hat
- 2026-10-30 Fix available: RHSA-2026:92509 · Red Hat
- 2026-10-30 Fix available: RHSA-2026:92497 · Red Hat
- 2026-10-30 Fix available: RHSA-2026:92480 · Red Hat
- 2026-10-30 Fix available: Red Hat OpenShift Service Mesh 3.0, Red Hat OpenShift Service Mesh 3.1, Red Hat OpenShift Service Mesh 3.2 +1 · Red Hat
- 2026-10-30 Affected versions changed · Red Hat
- 2026-10-31 Fix available: RHSA-2026:92516 · Red Hat
- 2026-10-31 Fix available: Red Hat OpenShift Service Mesh 3.4 · Red Hat
- 2026-11-06 Affected versions changed · Red Hat
- 2026-11-07 EPSS moved to the 50th–90th percentile
References
More Go standard library vulnerabilities
- TI-2020-00578 Improper certificate validation in Microsoft Windows KEVCVSS 3.1HIGH 8.1
- TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
- TI-2023-24278 HTTP/2 CONTINUATION flood in net/http CVSS 3.1HIGH 7.5
- TI-2018-05208 The "go get" implementation in Go 1.9.4, when the -insecure command-line option is used… CVSS 3.1HIGH 8.8
- TI-2024-16309 Panic when parsing invalid palette-color images in golang.org/x/image CVSS 3.1HIGH 7.5
- TI-2022-20112 Request smuggling due to improper request handling in golang.org/x/net/http2/h2c CVSS 3.1HIGH 7.5
Sources
- CVE-2026-78663 · CVE Program
- CVE-2026-78663 · NVD
- FIRST EPSS
- CVE-2026-78663 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences