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Fencer Vulns
medium 6.8

CVE-2026-47775 json

Envoy OAuth2 Filter: Padding Oracle via AES-256-CBC Cookie Decryption

published 2026-06-26 4 mo ago modified 2026-10-25 14 d ago also BIT-envoy-2026-47775 , EUVD-2026-39817 , GHSA-396h-jpq4-vc7p

cvss
6.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 12%
public exploits
0
none known

Summary

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.

Patch / fix

  • bitnami envoy 1.35.11, 1.36.7, 1.37.3, 1.38.1
  • envoyproxy envoy 1.35.11, 1.36.7, 1.37.3, 1.38.1
  • istioctl openSUSE Tumbleweed 1.30.2-1.1

opensuse advisories openSUSE-SU-2026:11141-1

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
4 mo ago

Exploit prediction

0.22% chance of exploitation in the next 30 days, higher than 12% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/envoyproxy/envoy/security/advisories/GHSA-396h-jpq4-vc7p referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
OSV 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
bitnami envoy
<1.35.11
>=1.36.0, <1.36.7
>=1.37.0, <1.37.3
>=1.38.0, <1.38.1
1.35.11
1.36.7
1.37.3
1.38.1

Affected products

  • envoyproxy envoy

Classification

Weakness
  • CWE-209 Generation of Error Message Containing Sensitive Information
  • CWE-327 Use of a Broken or Risky Cryptographic Algorithm

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.