CVE-2026-47775

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

MEDIUM

6.8

CVSS Score

Published: June 26, 2026 at 05:23 PM UTC

Updated: October 25, 2026 at 05:10 PM UTC

1 product affected across 1 vendorEnvoy

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Severity

MEDIUM6.8

Exploit prediction

EPSS 0.2%

SSVC

PoC

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Envoy · Envoyproxy

95%

1.35.0 ≤ v < 1.35.111.36.0 ≤ v < 1.36.71.37.0 ≤ v < 1.37.31.38.0 ≤ v < 1.38.1

Affected range stops below 1.35.11, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.36.7, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.37.3, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.38.1, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://github.com/envoyproxy/envoy/security/advisories/GHSA-396h-jpq4-vc7p

References (1)

x_refsource_CONFIRMExploitVendor AdvisoryMitigation

Source: cverecord

https://github.com/envoyproxy/envoy/security/advisories/GHSA-396h-jpq4-vc7p

SSVC — Action Prioritization

SSVCPoCNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.8MEDIUMGitHub_M

Attack Vector: NETWORK
Complexity: HIGH
Privileges: NONE
User Interaction: REQUIRED
Scope: UNCHANGED
Confidentiality: HIGH
Integrity: HIGH
Availability: NONE

Vector?

Quick Info

StatusANALYZED

CWE

CWE-209CWE-327

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