CVE-2025-62504
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 · uneditedEnvoy is an open source edge and service proxy. Envoy versions earlier than 1.36.2, 1.35.6, 1.34.10, and 1.33.12 contain a use-after-free vulnerability in the Lua filter. When a Lua script executing in the response phase rewrites a response body so that its size exceeds the configured per_connection_buffer_limit_bytes (default 1MB), Envoy generates a local reply whose headers override the original response headers, leaving dangling references and causing a crash. This results in denial of service. Updating to versions 1.36.2, 1.35.6, 1.34.10, or 1.33.12 fixes the issue. Increasing per_connection_buffer_limit_bytes (and for HTTP/2 the initial_stream_window_size) or increasing per_request_buffer_limit_bytes / request_body_buffer_limit can reduce the likelihood of triggering the condition but does not correct the underlying memory safety flaw.
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 confidenceEnvoy versions before 1.36.2, 1.35.6, 1.34.10, and 1.33.12 have a use-after-free vulnerability in the Lua filter. When a Lua script executing in the response phase rewrites a response body to exceed the per_connection_buffer_limit_bytes (default 1MB), Envoy generates a local reply with overriding headers that leave dangling references, causing a crash and denial of service.
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< 1.33.12>= 1.34.0, < 1.34.10>= 1.35.0, < 1.35.6>= 1.36.0, < 1.36.2CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Check Envoy versionRun 'envoy --version' or look for version in Envoy's admin /server_info endpoint. Compare the version number to the affected ranges: < 1.33.12, 1.34.0-1.34.9, 1.35.0-1.35.5, or 1.36.0-1.36.1.Affected if The installed version falls within any of the vulnerable version ranges.
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Identify Lua filter usage in configurationReview Envoy's configuration (static or dynamic) and search for any 'lua' filter entries in the filter chain. Look for 'lua' in the 'filters' section of the listener or route configuration.Affected if A Lua filter is configured and loaded in the Envoy instance.
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Check for response phase Lua scriptsExamine the Lua filter configuration for scripts that execute in the 'response' phase (or 'http_response' phase in newer Envoy versions). Look for 'route_config' or 'inline_code' blocks that include response handling logic.Affected if Lua scripts are configured to execute in the response phase.
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Inspect buffer limit configurationCheck Envoy configuration for 'per_connection_buffer_limit_bytes' setting at the listener level, or 'per_request_buffer_limit_bytes' at the upstream connection level. If not explicitly set, the default is 1048576 bytes (1MB).Affected if The configured buffer limit is low enough that a modified response body could exceed it, or the default 1MB limit is in effect.
An affected Envoy version combined with a Lua filter running scripts in the response phase creates the condition where a large body rewrite can trigger the use-after-free.
Generated from the published advisory. Verify against your own configuration.
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 · scoped1.33.121.34.101.35.6
Upgrade Envoy to version 1.36.2, 1.35.6, 1.34.10, or 1.33.12 to patch the memory safety flaw. Alternatively, increasing buffer limits (per_connection_buffer_limit_bytes, per_request_buffer_limit_bytes) can reduce trigger likelihood but does not fix the underlying vulnerability.
Upgrade to Envoy 1.33.12, 1.34.10, 1.35.6, or 1.36.2 (depending on your current version branch)
- 1. Identify the current Envoy version currently deployed (e.g., envoy --version)
- 2. Determine which version branch you are currently on (1.33.x, 1.34.x, 1.35.x, or 1.36.x)
- 3. Plan an upgrade to the corresponding fixed release: upgrade to 1.33.12 if on 1.33.x, 1.34.10 if on 1.34.x, 1.35.6 if on 1.35.x, or 1.36.2 if on 1.36.x
- 4. Review the Envoy release notes for the target version to check for any breaking changes or behavioral changes relevant to your deployment
- 5. Test the upgrade in a staging or non-production environment to verify compatibility with your Lua scripts and configuration
- 6. Deploy the upgraded version to production
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-62504 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-62504 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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