CVE-2023-54356

Kyverno 1.9.4 and earlier advertise and accept legacy 3DES cipher suites (TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA and TLS_RSA_WITH_3DES_EDE_CBC_SHA) on their TLS endpoints, relying on a 64-bit block cipher that is vulnerable to the Sweet32 attack (CVE-2016-2183). An attacker who can sustain or observe a very long-lived TLS connection carrying a large volume of traffic with a Kyverno endpoint could exploit this to recover small amounts of plaintext from the encrypted session. The practical impact is limited disclosure of fragments of session data, not remote code execution or full system compromise, and exploitation requires unusually long connections with high traffic volume. Anyone running Kyverno 1.9.4 or earlier — typically deployed as an admission-controller policy engine inside Kubernetes clusters — is affected. No public exploits or PoCs are known, the issue is not in CISA KEV, and EPSS estimates only a 0.1% probability of exploitation in the next 30 days.

What to do: Upgrade to Kyverno 1.9.5 or 1.10.0 (or later), which remove the insecure 3DES cipher suites. If upgrading must wait, configure Kyverno's TLS endpoints to advertise only modern 128-bit-or-stronger AEAD cipher suites (e.g., AES-GCM) and disable 3DES. Check which cipher suites your clients actually negotiate with Kyverno's endpoints and prioritize environments where long-lived, high-volume TLS connections terminate there.