CVE-2025-66220Published

Envoy’s TLS certificate matcher for `match_typed_subject_alt_names` may incorrectly treat certificates containing an embedded null byte

Collected exploitation and prediction evidence

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

cve-program · CVE-2025-66220

Published

Envoy is a high-performance edge/middle/service proxy. In 1.33.12, 1.34.10, 1.35.6, 1.36.2, and earlier, Envoy’s mTLS certificate matcher for match_typed_subject_alt_names may incorrectly treat certificates containing an embedded null byte (\0) inside an OTHERNAME SAN value as valid matches.

Source published: 3 Dec 2025 18:31:50 UTC
Source modified: 3 Dec 2025 19:10:53 UTC
Observed here: 23 Oct 2026 15:48:27 UTC
Source terms: CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

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CVSS 3.1 · 5.0 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:N

euvd · EUVD-2025-201090

Published

EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: Dec 3, 2025, 6:31:50 PM

dateUpdated: Dec 3, 2025, 7:10:53 PM

Source published: Dec 3, 2025, 6:31:50 PM (timezone not stated)
Source modified: Dec 3, 2025, 7:10:53 PM (timezone not stated)
Observed here: 11 Nov 2026 14:08:44 UTC
Source terms: ENISA EUVD · source terms and attribution apply

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EUVD CVSS 3.1 · 5.0 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:N

nvd · CVE-2025-66220

Published

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Analyzed

Weakness classifications: CWE-170

Original publisher date fields

published: 2025-12-03T19:15:58.010

lastModified: 2026-09-25T23:10:00.463

1 source CPE criteria · context only

cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*

The original JSON retains the logical configuration operators, exclusions and version bounds.

Source published: 3 Dec 2025 19:15:58 UTC
Source modified: 25 Sep 2026 23:10:00 UTC
Observed here: 25 Oct 2026 03:17:36 UTC
Source terms: NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 5.0 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:N

CVSS 3.1 · [email protected] · Primary · 7.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N

osv · GHSA-rwjg-c3h2-f57p

Published

### Summary Envoy’s mTLS certificate matcher for `match_typed_subject_alt_names` may incorrectly treat certificates containing an embedded null byte (\0) inside an `OTHERNAME` SAN value as valid matches. ### Details This occurs when the SAN is encoded as a `BMPSTRING` or `UNIVERSALSTRING`, and its UTF-8 conversion result is truncated at the first null byte during string assignment. As a result, `"victim\0evil"` may match an exact: `"victim"` rule and be accepted by Envoy. ### PoC Create a CA and a server certificate signed by that CA. Create two client certificates signed by the same CA: client_evil with OTHERNAME BMPSTRING = "evil" client_null with OTHERNAME BMPSTRING = "victim\0evil" Configure Envoy with require_client_certificate: true and a match_typed_subject_alt_names entry for the OTHERNAME OID with matcher.exact: "victim". Connect without a client cert → connection rejected. Connect with client_evil → connection rejected. Connect with client_null → connection accepted (but shouldn't!). ### Impact An attacker who can obtain a trusted client certificate with a null byte embedded in an OTHERNAME SAN can exploit this vulnerability. The practical impact is unauthorized impersonation of the matched identity, enabling access to services or APIs protected by that exact OTHERNAME check. ### Credit [[email protected]](mailto:[email protected])

Source published: 5 Dec 2025 18:14:02 UTC
Source modified: 6 Dec 2025 12:29:15 UTC
Observed here: 24 Oct 2026 13:19:41 UTC
Source terms: GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:N

Publisher rating · MODERATE