CVE-2026-47775

Summary

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.

Affected Software

VendorProductVersion RangeStatus
envoyproxyenvoy>= 1.38.0, < 1.38.1affected
envoyproxyenvoy>= 1.37.0, < 1.37.3affected
envoyproxyenvoy>= 1.36.0, < 1.36.7affected
envoyproxyenvoy< 1.35.11affected

Weaknesses

  • CWE-209: CWE-209: Generation of Error Message Containing Sensitive Information
  • CWE-327: CWE-327: Use of a Broken or Risky Cryptographic Algorithm

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: poc
    • Automatable: no
    • Technical Impact: total

Additional References

References