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EnvoyApplication · Envoyproxy

CVE-2023-35945

HIGH · 7.5 CVSS v3.1 Published 2023-07-13
Fix available
A fix is available. Upgrade to 1.23.11 / 1.24.9 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Envoy's HTTP/2 codec leaks header maps and bookkeeping structures when receiving RST_STREAM immediately followed by GOAWAY frames from an upstream server. In nghttp2, cleanup of pending requests due to GOAWAY skips de-allocation of the bookkeeping structure and pending compressed header because the error return code path is taken when the connection is already marked for not sending more requests, leaving the clean-up code unreachable.

MitigationUpgrade Envoy to patched versions 1.26.3, 1.25.8, 1.24.9, or 1.23.11 (or later) to remediate the memory leak that can cause denial of service through memory exhaustion.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
EnvoyApplication
Affected:< 1.23.11>= 1.24.0, < 1.24.9>= 1.25.0, < 1.25.8>= 1.26.0, < 1.26.3
Nghttp2Application
Affected:< 1.55.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Envoy version
    Run 'envoy --version' or check the Docker/service metadata for the deployed Envoy version
    Affected if The version falls into any of these ranges: < 1.23.11, >= 1.24.0 and < 1.24.9, >= 1.25.0 and < 1.25.8, or >= 1.26.0 and < 1.26.3
  2. Identify nghttp2 version linked to Envoy or standalone
    Run 'ldd $(which envoy) | grep nghttp2' to find the linked library, then check the library file version, or check nghttp2 --version if installed separately
    Affected if nghttp2 version is present and is < 1.55.1
  3. Verify HTTP/2 upstream configuration
    Review Envoy configuration files (yaml/json) for upstream cluster definitions with 'http2' or 'http/2' protocol settings, or check if 'http2_protocol_options' is configured
    Affected if Envoy is configured to use HTTP/2 for upstream connections - the vulnerability only triggers when receiving RST_STREAM followed by GOAWAY from an upstream server

You are affected if you are running a vulnerable Envoy or nghttp2 version AND have HTTP/2 enabled for upstream connections that could receive the specific frame sequence (RST_STREAM then GOAWAY) from backend servers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.23.11 / 1.24.9 / 1.25.8 or later
Fixed in 1.23.111.24.91.25.8
Interim mitigation

Upgrade Envoy to patched versions 1.26.3, 1.25.8, 1.24.9, or 1.23.11 (or later) to remediate the memory leak that can cause denial of service through memory exhaustion.

Recommended fix High confidence

1.26.3 (latest stable fix for 1.26.x branch)

  1. 1. Identify current Envoy version using `envoy --version` or checking the deployment manifests
  2. 2. Determine the appropriate upgrade version based on current version: if < 1.23.11 upgrade to 1.23.11; if >= 1.24.0 and < 1.24.9 upgrade to 1.24.9; if >= 1.25.0 and < 1.25.8 upgrade to 1.25.8; if >= 1.26.0 and < 1.26.3 upgrade to 1.26.3
  3. 3. If using nghttp2 as a dependency, also upgrade nghttp2 to version 1.55.1 or later
  4. 4. Test the upgrade in a staging environment before production deployment
  5. 5. Deploy the upgraded Envoy version
  6. 6. Monitor memory usage to confirm the leak is resolved
Caveat Patch releases (z in x.y.z) typically have minimal breaking changes; review Envoy release notes for any behavioral changes

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Envoy Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
9.0 hours of engineering $1,570
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,512.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-35945 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data