What is the CVSS score of EUVD-2026-39817?

EUVD-2026-39817 has a CVSS 3.1 base score of 6.8 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N. EPSS exploitation probability: 0.2%.

Is there a patch available for EUVD-2026-39817?

Yes, a patch is available for EUVD-2026-39817. Update the affected software to the latest version immediately.

Envoy Proxy EUVD-2026-39817

| CVE-2026-47775 MEDIUM

Error Message Information Leak (CWE-209)

2026-06-26 GitHub_M

Oracle Microsoft Information Disclosure Envoy

6.8

CVSS 3.1 · Vendor: GitHub_M

Severity by source

Vendor (GitHub_M) PRIMARY

6.8 MEDIUM

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

vuln.today AI

6.8 MEDIUM

Network attack against /callback; AC:H reflects dual prerequisite of cookie and code theft; UI:R requires active victim OAuth session; C:H/I:H for token-based account takeover; A:N as no availability impact.

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

4.0 AV:N/AC:H/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

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

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Lifecycle Timeline

Patch available

Jun 26, 2026 - 19:02 EUVD

Analysis Generated

Jun 26, 2026 - 18:31 vuln.today

CVE Published

Jun 26, 2026 - 17:23 cve.org

MEDIUM 6.8

DescriptionCVE.org

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.

AnalysisAI

The OAuth2 HTTP filter in Envoy Proxy prior to versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1 implements AES-256-CBC encryption for the PKCE CodeVerifier cookie without any authentication tag, creating a classic padding oracle through differential HTTP responses on the /callback endpoint. An attacker who obtains the victim's encrypted CodeVerifier cookie and a stolen authorization code can recover the plaintext PKCE code_verifier in approximately 6,200 crafted requests (~100 seconds), then complete the OAuth token exchange to hijack the victim's access token. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access

Steal victim's encrypted CodeVerifier cookie and authorization code

Delivery

Submit ~6,200 crafted CBC ciphertexts to /callback endpoint

Exploit

Observe HTTP 302/401 differential responses as padding oracle

Execution

Recover plaintext PKCE code_verifier byte-by-byte

Persist

Exchange recovered code_verifier plus stolen authorization code with authorization server

Impact

Obtain victim OAuth access token

Access

Steal victim's encrypted CodeVerifier cookie and authorization code

Delivery

Submit ~6,200 crafted CBC ciphertexts to /callback endpoint

Exploit

Observe HTTP 302/401 differential responses as padding oracle

Execution

Recover plaintext PKCE code_verifier byte-by-byte

Persist

Exchange recovered code_verifier plus stolen authorization code with authorization server

Impact

Obtain victim OAuth access token

Vulnerability AssessmentAI

Exploitation	Exploitation requires that the target Envoy instance has the OAuth2 HTTP filter explicitly configured - deployments not using this filter are completely unaffected regardless of Envoy version. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment	The CVSS 6.8 score with AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N accurately reflects the attack's dual prerequisites - obtaining the encrypted cookie and a stolen authorization code - which together constitute the AC:H classification, and the requirement for an active victim OAuth session (UI:R). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario	An attacker targeting a user authenticating through an Envoy-fronted application intercepts or steals the victim's encrypted CodeVerifier cookie alongside the OAuth authorization code - for example, via a network-adjacent position or cookie-theft XSS on the initiating application. The attacker then submits approximately 6,200 byte-manipulated ciphertexts to Envoy's /callback endpoint over roughly 100 seconds, using the HTTP 302/401 differential responses as a padding oracle to recover the plaintext PKCE code_verifier. …
Remediation	Upgrade Envoy to one of the vendor-confirmed fixed releases: 1.35.11, 1.36.7, 1.37.3, or 1.38.1, which replace the unauthenticated AES-256-CBC scheme with an authenticated encryption implementation, eliminating the padding oracle. … Detailed patch versions, workarounds, and compensating controls in full report.