CVE-2026-47775
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.
Does this matter?
Lower severity and a low EPSS score (0.22%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 6.8 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
- EPSS
- 0.22% probability · 12th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-209, CWE-327
- Affected
- envoyproxy/envoy
- Source
- security-advisories@github.com
References
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-396h-jpq4-vc7pExploit, Vendor Advisory, Mitigation
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-396h-jpq4-vc7pExploit, Vendor Advisory, Mitigation
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.