CVE-2026-47775
CVE-2026-47775 — Envoy OAuth2 Filter: Padding Oracle via AES-256-CBC Cookie Decryption
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.
Published Updated Sources: cvelistV5, GitHub_M
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.
Exploitation
Unreported
no source claims exploitation
EPSS
0%
chance of exploitation in 30 days
CVSS base
6.8
MEDIUM
CISA SSVC assessment
Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.
Exploitation
PoC
none · proof-of-concept · active
Automatable
No
can an attacker script all four kill-chain steps
Technical impact
Total
partial · total control of the vulnerable component
Affected scope
The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.
Vendors (1)
Products (1)
Every base score collected
Sources score independently and disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Source |
|---|---|---|---|---|---|
| 6.8 | CVSS 3.1 | MEDIUM | — | — | cvelistV5 |
Weakness & attack patterns
- CWE-209
- CWE-327
Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.
- T1036.001Masquerading: Invalid Code Signature
- T1553.002Subvert Trust Controls: Code Signing
Detection
Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.
- Search application, proxy, and WAF logs for requests touching /decrypt(), /callback.
References
1 on the record
- github.com/envoyproxy/envoy/security/advisories/GHSA-396h-jpq4-vc7p
x_refsource_CONFIRM
Elsewhere on this site
- envoyproxyevery CVE for this vendor
- CWE-209other pages naming this weakness
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.