Envoy OAuth2 Filter: Padding Oracle via AES-256-CBC Cookie Decryption_CVE-2026-47775

{
    "lastseen": "",
    "description": "Envoy 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, the OAuth2 HTTP filter's encrypt()/decrypt() functions use AES-256-CBC without an authentication tag (no HMAC, no AEAD). The /callback endpoint returns HTTP 302 on successful decryption and HTTP 401 on padding failure, creating a padding oracle. An attacker who obtains the encrypted CodeVerifier cookie can recover the plaintext PKCE code_verifier in ~6,200 requests (~100 seconds), then exchange it with a stolen authorization code to obtain the victim's access token. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1.",
    "published": "2026-06-26T17:23:51.663Z",
    "modified": "2026-06-26T17:23:51.663Z",
    "type": "cve",
    "title": "Envoy OAuth2 Filter: Padding Oracle via AES-256-CBC Cookie Decryption",
    "source": "GitHub_M",
    "references": "https://github.com/envoyproxy/envoy/security/advisories/GHSA-396h-jpq4-vc7p",
    "id": "CVE-2026-47775",
    "bulletinFamily": "",
    "cwe": [
        "CWE-209",
        "CWE-327"
    ],
    "cvelist": null,
    "sourceData": "envoyproxy envoy >= 1.38.0, < 1.38.1\nenvoyproxy envoy >= 1.37.0, < 1.37.3\nenvoyproxy envoy >= 1.36.0, < 1.36.7\nenvoyproxy envoy < 1.35.11",
    "sourceHref": "",
    "cvss": {
        "score": 6.8,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N",
        "version": "3.1"
    },
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    },
    "href": "",
    "category_name": "CVE",
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    "product": "envoy",
    "version": ">= 1.38.0, < 1.38.1",
    "vendor": "envoyproxy",
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}