CVE-2023-35945 | Envoy vulnerable to HTTP/2 memory leak in nghttp2 codec

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.

Published: 2023-07-13 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-35945 is rated Moderate Risk (52.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.11%). EPSS rose +1.03% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2023-35945

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.07% 1.11% +1.03%
2 2025-03-30 0.30% 0.07% -0.23%
3 2025-03-29 — 0.30% —

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-35945

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2023-35945

OS Trackers for CVE-2023-35945

vendor priority summary link
alpine high CVE-2023-35945: 1 source package rows (nghttp2); 1 state rows across 1 repos (3.17-main); fixed 1, open 0. https://security.alpinelinux.org/vuln/CVE-2023-35945
redhat high — https://access.redhat.com/security/cve/CVE-2023-35945
suse high CVE-2023-35945 severity important: SUSE including 308 source package names (1.2.3-2.2.19:libnghttp2-14-1.40.0-150200.9.1, 1.2.3-3.2.19:libnghttp2-14-1.40.0-150200.9.1, …), 618 product×package rows across 248 product lines (Container bci/bci-init, Container bci/golang, … (248 product lines)): Fixed 438, Known Affected 180. https://www.suse.com/security/cve/CVE-2023-35945/

Affected software / configurations for CVE-2023-35945

Vendor Product Version Raw CPE
envoyproxy envoy < 1.23.11 cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*
envoyproxy envoy >= 1.24.0, < 1.24.9 cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*
envoyproxy envoy >= 1.25.0, < 1.25.8 cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*
envoyproxy envoy >= 1.26.0, < 1.26.3 cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*
nghttp2 nghttp2 < 1.55.1 cpe:2.3:a:nghttp2:nghttp2:*:*:*:*:*:*:*:*

References for CVE-2023-35945

cvelogic Threat Intelligence