CVE-2026-48497
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 designed for cloud-native applications. Prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1, in cases where UDP DNS filter is configured with local resolution containing a name with the length of 255 octets or remote resolution for a name of 255 octets long can complete successfully, a query with such name will result in abnormal process termination. The abnormal process termination is triggered by an invalid runtime precondition that the query name is strictly less than 255 octets, contradicting DNS specification rfc1035#section-2.3.4 that the name can be 255 or less octets. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1.
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 confidenceIn Envoy's UDP DNS filter, an invalid runtime precondition incorrectly asserts that DNS query names must be strictly less than 255 octets, contradicting RFC 1035 which permits names of 255 octets or less. When a DNS query with a 255-octet name is processed, this triggers an assertion failure causing abnormal process termination, resulting in 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< 1.35.13>= 1.36.0, < 1.36.9>= 1.37.0, < 1.37.5>= 1.38.0, < 1.38.3CVSS 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 query the `/server_info` admin endpoint to retrieve the installed Envoy version.Affected if Version is < 1.35.13, >= 1.36.0 and < 1.36.9, >= 1.37.0 and < 1.37.5, or >= 1.38.0 and < 1.38.3
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Identify if UDP DNS filter is configuredReview Envoy's static configuration or dynamic listeners configuration. Look for a listener filter or network filter of type `envoy.filters.udp.dns_filter` or similar UDP DNS filter extension.Affected if A UDP DNS filter is present in the Envoy configuration
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Verify UDP DNS filter is activeCheck listener status via `/listeners` admin endpoint or configuration dump. Confirm the DNS filter is bound to a UDP listener and receiving traffic.Affected if The UDP DNS filter is actively bound to a UDP listener handling DNS traffic
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Assess exposure to external DNS queriesDetermine if the UDP listener with the DNS filter is exposed to untrusted networks or can receive DNS queries from clients. Check network access controls, firewall rules, and listener bind address.Affected if The UDP DNS filter listener is reachable by external or untrusted clients who could send crafted DNS queries
You are affected if your Envoy version falls within the vulnerable ranges and a UDP DNS filter is actively handling DNS queries from potential attackers.
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 · scoped1.35.131.36.91.37.5
Upgrade Envoy to version 1.35.11, 1.36.7, 1.37.3, or 1.38.1 or later, which contain the corrected runtime precondition check. Until upgrade, consider restricting or filtering UDP DNS traffic reaching the Envoy instance.
Upgrade to Envoy 1.35.13, 1.36.9, 1.37.5, or 1.38.3 (choose the release line matching your current version)
- 1. Identify the current Envoy proxy version in use by checking the deployed binaries or container images
- 2. Based on the current version, determine the appropriate upgrade target from the fixed releases: 1.35.13, 1.36.9, 1.37.5, or 1.38.3
- 3. Plan the upgrade, ensuring compatibility with existing configuration and dependencies
- 4. For containerized deployments, update the image tag to the fixed version (e.g., envoyproxy/envoy:v1.38.3)
- 5. For binary deployments, download the appropriate fixed release from the Envoy GitHub releases page
- 6. Test the upgrade in a staging environment before deploying to production
- 7. Deploy the upgraded Envoy version and verify the DNS filter functions correctly with 255-octet names
- 8. Monitor logs for any abnormal process terminations to confirm the fix is effective
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-48497 — 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-2026-48497 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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