Description

Kyverno versions 1.9.4 and earlier support insecure 3DES cipher suites (TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA and TLS_RSA_WITH_3DES_EDE_CBC_SHA) on their TLS endpoints. These 64-bit block ciphers are vulnerable to the Sweet32 attack (CVE-2016-2183), which, over very long-lived TLS connections carrying large volumes of traffic, could allow an attacker to recover small amounts of plaintext. The issue is fixed in Kyverno 1.9.5 and 1.10.0.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "3.7",
  "pubDate": "2026-09-01T12:17:11.220Z",
  "pubdate": "2026-09-01T12:17:11.220Z",
  "executiveSummary": "Kyverno versions 1.9.4 and earlier are susceptible to a security vulnerability related to the use of deprecated and insecure 3DES (Triple Data Encryption Algorithm) cipher suites within their TLS communication endpoints.\nThe identified cipher suites, specifically TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA and TLS_RSA_WITH_3DES_EDE_CBC_SHA, are inherently vulnerable to the Sweet32 attack, tracked as CVE-2016-2183.\nThis vulnerability allows a remote attacker to exploit the inherent birthday bound weaknesses of 64-bit block ciphers.\nThe primary risk involves the potential recovery of plaintext data through cryptanalytic analysis of intercepted traffic, provided the attacker can sustain a long-lived TLS connection with a significant volume of encrypted data.\nWhile the prerequisites for exploitation are demanding, the continued support for these ciphers violates modern cryptographic standards and presents an unnecessary security risk to the integrity and confidentiality of communication within the Kyverno environment.\nOrganizations using affected Kyverno versions are advised to upgrade to the remediated versions to neutralize this threat.",
  "technicalDetails": "The vulnerability originates from the Kyverno TLS configuration, which permits the negotiation of 3DES-based cipher suites. The underlying issue is rooted in the 64-bit block size of the 3DES algorithm, which makes it fundamentally susceptible to collision attacks when utilizing Cipher Block Chaining (CBC) modes.\nCVE-2016-2183, commonly referred to as the Sweet32 attack, exploits the birthday paradox to recover plaintext. In a TLS session using 3DES, the security margin is constrained by the block size rather than the key length. Because the block size is only 64 bits, collisions in the encrypted data blocks become statistically likely after approximately 2^32 blocks of data have been encrypted with the same session key.\nThe attack flow requires an attacker to position themselves as a Man-in-the-Middle (MitM) or otherwise gain the capability to observe and influence high-volume traffic between the client and the Kyverno server. The attacker facilitates a long-lived TLS connection, forcing the exchange of a massive amount of data. By monitoring for specific collision patterns in the ciphertext that correspond to the known structure of sensitive data (such as HTTP headers or cookies), an attacker can perform differential cryptanalysis to deduce the plaintext content.\nThe exploitation process occurs in several phases: first, the attacker monitors the session until the volume of transferred data reaches the birthday bound threshold; second, the attacker identifies a collision where two ciphertext blocks are identical; third, the attacker applies XOR operations between the two blocks and the known plaintext to reveal the underlying secret data. Given the iterative nature of this attack, it necessitates persistent and heavy traffic flow to achieve successful data recovery.\nThe vulnerable components are the TLS endpoints hosted by Kyverno, which negotiate connection parameters and allow the insecure 3DES ciphers during the handshake process. Affected versions include all iterations up to and including 1.9.4. No specific authentication or privilege escalation is required to initiate the attack beyond the ability to intercept network traffic and sustain a connection. Post-exploitation impact is limited to the decryption of data transmitted over the affected TLS session, which may include authentication tokens or sensitive metadata depending on the traffic profile."
}