Envoy OAuth2 Filter: Padding Oracle via AES-256-CBC Cookie Decryption

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Summary

CVECVE-2026-47775
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-26 18:16:59 UTC
Updated2026-06-26 19:50:17 UTC
DescriptionEnvoy 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.

Risk And Classification

Primary CVSS: v3.1 6.8 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

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

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
3.1CNADECLARED6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Envoyproxy Envoy affected >= 1.38.0, < 1.38.1 Not specified
CNA Envoyproxy Envoy affected >= 1.37.0, < 1.37.3 Not specified
CNA Envoyproxy Envoy affected >= 1.36.0, < 1.36.7 Not specified
CNA Envoyproxy Envoy affected < 1.35.11 Not specified

References

ReferenceSourceLinkTags
github.com/envoyproxy/envoy/security/advisories/GHSA-396h-jpq4-vc7p [email protected] github.com
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