TI-2023-18006 Aliases CVE-2023-35945

Envoy vulnerable to HTTP/2 memory leak in nghttp2 codec

HIGH 72CWE-400Published 2023-07-13 · Updated 2026-10-14

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-400.

Summary

Envoy is a cloud-native high-performance edge/middle/service proxy. Envoy’s HTTP/2 codec may leak a header map and bookkeeping structures upon receiving `RST_STREAM` immediately followed by the `GOAWAY` frames from an upstream server. In nghttp2, cleanup of pending requests due to receipt of the `GOAWAY` frame skips de-allocation of the bookkeeping structure and pending compressed header. The error return [code path] is taken if connection is already marked for not sending more requests due to `GOAWAY` frame. The clean-up code is right after the return statement, causing memory leak. Denial of service through memory exhaustion. This vulnerability was patched in versions(s) 1.26.3, 1.25.8, 1.24.9, 1.23.11.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.01652 76th percentileScored 2026-11-07

Fix Fixed envoy (envoyproxy): 1.26.3, 1.25.8, 1.24.9 +1Red Hat: 3 advisories

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: Yes
Technical impact: Partial

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
envoyproxy	envoy	1.26.0 to before 1.26.3; 1.25.0 to before 1.25.8; 1.24.0 to before 1.24.9; 1.23.0 to before 1.23.11	1.26.3, 1.25.8, 1.24.9, 1.23.11	Patch available	CNA

envoy Vendorenvoyproxy Affected 1.26.0 to before 1.26.3; 1.25.0 to before 1.25.8; 1.24.0 to before 1.24.9; 1.23.0 to before 1.23.11 Fixed in 1.26.3, 1.25.8, 1.24.9, 1.23.11 Patch available CNA

CPE configurations NVD · 2

CPE	Versions	Role	Vendor
cpe:2.3:a:envoyproxy:envoy::::::::	before 1.23.11; 1.24.0 to before 1.24.9; 1.25.0 to before 1.25.8; 1.26.0 to before 1.26.3	Vulnerable	envoyproxy
cpe:2.3:a:nghttp2:nghttp2::::::::	before 1.55.1	Vulnerable	nghttp2

cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* Versions before 1.23.11; 1.24.0 to before 1.24.9; 1.25.0 to before 1.25.8; 1.26.0 to before 1.26.3 Vulnerable ·envoyproxy
cpe:2.3:a:nghttp2:nghttp2:*:*:*:*:*:*:*:* Versions before 1.55.1 Vulnerable ·nghttp2

Remediation

Fix · CNA envoy (envoyproxy) Fixed in 1.26.3, 1.25.8, 1.24.9, 1.23.11

Red Hat 3 advisories

RHSA-2023:5175 Released 2023-09-14 · Red Hat rating Important
Red Hat OpenShift Service Mesh 2.2.10 security update
- RHOSSM 2.2 for RHEL 8 openshift-service-mesh/proxyv2-rhel8
RHSA-2023:4625 Released 2023-08-11 · Red Hat rating Important
Red Hat OpenShift Service Mesh Containers for 2.4.2 security update
- RHOSSM 2.4 for RHEL 8 openshift-service-mesh/proxyv2-rhel8
RHSA-2023:4624 Released 2023-08-11 · Red Hat rating Important
Red Hat OpenShift Service Mesh Containers for 2.3.6 security update
- RHOSSM 2.3 for RHEL 8 openshift-service-mesh/proxyv2-rhel8

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

Product	Status	Plan or fix
RHOSSM 2.2 for RHEL 8	Fixed	RHSA-2023:5175
RHOSSM 2.3 for RHEL 8	Fixed	RHSA-2023:4624
RHOSSM 2.4 for RHEL 8	Fixed	RHSA-2023:4625

Not affected: 4 products

RHOSSM 2.2 for RHEL 8
RHOSSM 2.3 for RHEL 8
RHOSSM 2.4 for RHEL 8
Red Hat JBoss Core Services

Timeline

2026-10-02 Threatist record created from CVE-2023-35945

References

Advisory 1

https://github.com/envoyproxy/envoy/security/advisories/GHSA-jfxv-29pc-x22r

Other 1

https://github.com/nghttp2/nghttp2/blob/e7f59406556c80904b81b593d38508591bb7523a/lib/nghttp2_session.c#L3346

TI-2026-79288 Out-of-bounds write in Google Brotli decoder KEVCVSS 4.0CRITICAL 9.2
TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
TI-2024-20001 HTTP/2: CPU exhaustion due to CONTINUATION frame flood CVSS 3.1HIGH 7.5
TI-2024-18524 HTTP/2: memory exhaustion due to CONTINUATION frame flood CVSS 3.1HIGH 7.5
TI-2023-12215 Envoy client may fake the header `x-envoy-original-path` CVSS 3.1CRITICAL 9.1
TI-2023-18002 Envoy vulnerable to OAuth2 credentials exploit with permanent validity CVSS 3.1CRITICAL 9.8

See all 126 →

Sources

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