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

> Attackers can exploit a padding oracle in Envoy's OAuth2 filter to recover PKCE code verifiers and steal user access tokens.

- **Severity:** Medium 6.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 26 Jun 2026
- **Updated:** 29 Jun 2026
- **Also known as:** BIT-envoy-2026-47775, GHSA-396h-jpq4-vc7p

## What is CVE-2026-47775?

CVE-2026-47775 is a medium-severity vulnerability in Envoyproxy Envoy, published on 26 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-327 (Use of a Broken or Risky Cryptographic Algorithm), CWE-209 (Generation of Error Message Containing Sensitive Information)

## Which versions are affected by CVE-2026-47775?

1 open source package ship an affected version, including envoy. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `envoy` | Bitnami | All versions | 1.35.11, 1.36.7, 1.37.3, 1.38.1 |

Products: Envoyproxy Envoy.

## How do I fix CVE-2026-47775?

Upgrade envoy to a fixed version for your release line: 1.35.11, 1.36.7, 1.37.3 or 1.38.1.

## Is CVE-2026-47775 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47775 exists.

## Other vulnerabilities in Envoyproxy Envoy

- [CVE-2022-29226](https://insights.sbomify.com/CVE-2022-29226/): Trivial authentication bypass in Envoy (critical 10.0)
- [CVE-2019-18801](https://insights.sbomify.com/CVE-2019-18801/): Memory corruption in n/a (critical 9.8)
- [CVE-2019-18802](https://insights.sbomify.com/CVE-2019-18802/): Security feature bypass in n/a (critical 9.8)
- [CVE-2020-35470](https://insights.sbomify.com/CVE-2020-35470/): Information disclosure in n/a (high 8.8)
- [CVE-2024-23324](https://insights.sbomify.com/CVE-2024-23324/): Envoy ext auth can be bypassed when Proxy protocol filter sets invalid UTF-8 metadata (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-47775 and fix it if it is affected.

What it is: CVE-2026-47775 is a medium-severity vulnerability in Envoyproxy Envoy, published on 26 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47775 exists.

Affected packages and fixed versions:
- envoy (Bitnami): affected all versions; fixed in 1.35.11, 1.36.7, 1.37.3, 1.38.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-47775/ (Markdown: https://insights.sbomify.com/CVE-2026-47775/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47775
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47775
- OSV: https://osv.dev/vulnerability/CVE-2026-47775

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-47775/
Summaries are generated and may contain mistakes; the official description above is the record.