CVE-2026-47775: Envoy OAuth2 HTTP filter padding oracle vulnerability

CVE-2026-47775 · Severity: medium · CVSS 6.8 · Published 2026-06-26

Envoy is a high-performance service proxy used to manage and secure network traffic for cloud applications. A security flaw in its OAuth2 authentication component allows an attacker to bypass security protections by exploiting how the system handles encrypted login data. If successful, an attacker could intercept a user's session and gain unauthorized access to their account and sensitive data.

Technologies: Envoy Proxy Envoy. Vendors: Envoy Proxy.

Quick answers

Is CVE-2026-47775 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-47775 being exploited in the wild.
How severe is CVE-2026-47775?
Medium severity, with a CVSS score of 6.8, published 26 June 2026.
Which products and versions are affected?
Envoy Proxy Envoy < 1.35.11, 1.36.0 to < 1.36.7, 1.37.0 to < 1.37.3, 1.38.0 to < 1.38.1.
Is there a fix for CVE-2026-47775?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-47775 attacked?
It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-47775?
Check whether you run Envoy Proxy Envoy at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The OAuth2 HTTP filter in Envoy uses AES-256-CBC for cookie encryption without an authentication tag (HMAC or AEAD). The `/callback` endpoint returns distinct HTTP status codes (302 for success vs. 401 for padding failure), creating a padding oracle. An attacker who intercepts a victim's 'CodeVerifier' cookie and authorization code can perform a padding oracle attack in approximately 6,200 requests to recover the plaintext PKCE code_verifier. This allows the attacker to exchange the stolen code for a valid access token. The fix involves migrating to AES-256-GCM and ensuring uniform error responses.

Affected products

  • Envoy Proxy Envoy < 1.35.11, 1.36.0 to < 1.36.7, 1.37.0 to < 1.37.3, 1.38.0 to < 1.38.1

Timeline

  • 2026-03-13: disclosed: Vulnerability discovered and verified with E2E exploit
  • 2026-03-15: other: Reported to Envoy GitHub Security Advisory
  • 2026-06-26: advisory: CVE-2026-47775 published

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.