CVE-2026-47775

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.

CVSS v3.1 Score

6.8

MEDIUM

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

EPSS — Exploit Prediction

0.0022

Probability of exploitation

0.12%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-209 CWE-209

CWE-327 CWE-327

Affected Products

Vendor	Product	Versions
envoyproxy	envoy	1.35.0 — 1.35.11
envoyproxy	envoy	1.36.0 — 1.36.7
envoyproxy	envoy	1.37.0 — 1.37.3
envoyproxy	envoy	1.38.0 — 1.38.1

References

Advisories & Patches

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

Exploits

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

Frequently Asked Questions

What is CVE-2026-47775? +

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. It has a CVSS v3.1 base score of 6.8 (MEDIUM).

How severe is CVE-2026-47775? +

CVE-2026-47775 has a CVSS v3.1 score of 6.8 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0022, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-47775? +

CVE-2026-47775 affects products from envoyproxy, specifically: envoy. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-47775? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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