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CVE-2026-47775— Envoy OAuth2 Filter: Padding Oracle via AES-256-CBC Cookie Decryption

Quick assessment

Affected
envoyproxy envoy
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Envoy Proxy Envoy是Envoy Proxy团队的应用网关。 Envoy Proxy Envoy 1.35.11之前版本、1.36.7之前版本、1.37.3之前版本和1.38.1之前版本存在安全漏洞，该漏洞源于OAuth2 HTTP filter的encrypt()/decrypt()函数使用AES-256-CBC但没有认证标签，创建了填充预言机，攻击者通过获取加密的CodeVerifier cookie可以恢复明文PKCE code_verifier并交换授权码获取访问令牌。

CVSS 6.8 · Medium EPSS 0.22% · P11

Affected Version Matrix 4

VendorProduct Version RangeStatus
envoyproxy envoy >= 1.38.0, < 1.38.1 affected
>= 1.37.0, < 1.37.3 affected
>= 1.36.0, < 1.36.7 affected
< 1.35.11 affected
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I. Basic Information for CVE-2026-47775

Vulnerability Information
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Vulnerability Title
Envoy OAuth2 Filter: Padding Oracle via AES-256-CBC Cookie Decryption
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过错误消息导致的信息暴露
Source: CVE Program / CVE List V5
Vulnerability Title
Envoy Proxy Envoy 信息泄露漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Envoy Proxy Envoy是Envoy Proxy团队的应用网关。 Envoy Proxy Envoy 1.35.11之前版本、1.36.7之前版本、1.37.3之前版本和1.38.1之前版本存在安全漏洞，该漏洞源于OAuth2 HTTP filter的encrypt()/decrypt()函数使用AES-256-CBC但没有认证标签，创建了填充预言机，攻击者通过获取加密的CodeVerifier cookie可以恢复明文PKCE code_verifier并交换授权码获取访问令牌。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
envoyproxy envoy >= 1.38.0, < 1.38.1 -

II. Public POCs for CVE-2026-47775

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III. Intelligence Information for CVE-2026-47775

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Vendor Advisories for CVE-2026-47775 (1)

Same Patch Batch · envoyproxy · 2026-06-26 · 14 CVEs total

CVE-2026-48743 7.5 HIGH Envoy: HTTP/3 to HTTP/1 request smuggling via headers-only request with nonzero Content-Le
CVE-2026-48042 7.5 HIGH Envoy: Stack overflow in destructor of highly nested JSON
CVE-2026-48044 7.5 HIGH Envoy Zstd Decompressor: Ratio Check at Wrong Loop Depth lead to memory explosion
CVE-2026-47220 7.5 HIGH Envoy: Segmentation fault when using %REQUESTED_SERVER_NAME% in log format
CVE-2026-47204 6.5 MEDIUM Envoy: grpc_stats filter segfault on Connect protocol requests to direct_response routes
CVE-2026-47207 6.5 MEDIUM Envoy crashes if multiple unexpected ext_proc responses are packed into one gRPC message
CVE-2026-47221 5.9 MEDIUM Envoy: Null pointer deref in internal redirects
CVE-2026-48497 5.9 MEDIUM Envoy: Abnormal process termination in DNS UDP filter
CVE-2026-48706 5.9 MEDIUM Envoy Heap Buffer Overflow in TcpStatsdSink
CVE-2026-47205 5.9 MEDIUM Envoy: ext_authz Use-After-Free during Stream Teardown with Per-Route Overrides
CVE-2026-48090 5.9 MEDIUM Envoy HTTP: OAuth2 filter late async token completion after stream teardown (UAF / crash r
CVE-2026-47692 4.8 MEDIUM Envoy: PROXY Protocol v2 header generator emits "skipped" TLVs, causing 65 KB attacker-con
CVE-2026-47778 4.4 MEDIUM Envoy: Embedded NUL in TLS DNS SAN Truncation in the Default TLS Certificate Validator. (A

IV. Related Vulnerabilities

Same product: envoy
Same vendor: envoyproxy
Same weakness: CWE-209

V. Comments for CVE-2026-47775

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