{"id":"BIT-envoy-2026-47775","summary":"Envoy OAuth2 Filter: Padding Oracle via AES-256-CBC Cookie Decryption","details":"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.","aliases":["CVE-2026-47775","GHSA-396h-jpq4-vc7p"],"modified":"2026-09-08T08:47:28.133709012Z","published":"2026-06-30T23:39:29.055Z","database_specific":{"severity":"Medium","cpes":["cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*"]},"references":[{"type":"ADVISORY","url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-396h-jpq4-vc7p"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-47775"}],"affected":[{"package":{"name":"envoy","ecosystem":"Bitnami","purl":"pkg:bitnami/envoy"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.35.11"},{"introduced":"1.36.0"},{"fixed":"1.36.7"},{"introduced":"1.37.0"},{"fixed":"1.37.3"},{"introduced":"1.38.0"},{"fixed":"1.38.1"}]}],"database_specific":{"source":"https://github.com/bitnami/vulndb/tree/main/data/envoy/BIT-envoy-2026-47775.json"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N"}]}],"schema_version":"1.9.0"}