CVE-2026-47775
MediumCVSS 6.8Exploitation Probability (EPSS)
Low risk11th percentile — higher than 11% of all known CVEs
Summary
Envoy prior to versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1 has a vulnerability in the OAuth2 filter where encrypt()/decrypt() functions use AES-256-CBC without an authentication tag. An attacker can exploit a padding oracle on the /callback endpoint to recover the plaintext PKCE code_verifier from the encrypted CodeVerifier cookie.
Risk Assessment
The risk involves potential theft of the victim's access token by recovering the code_verifier and exchanging it with a stolen authorization code, leading to unauthorized access to protected resources.
Recommendation
Immediately upgrade Envoy to versions 1.35.11, 1.36.7, 1.37.3, or 1.38.1, which contain the fix for this vulnerability.
Original NVD description (English source)
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.