Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-08-05T11:55:38 libkcapi: IV reuse in libkcapi one-shot symmetric cipher chunking causes cipher state reset across chunk boundaries 6.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N CWE-330

A flaw was found in libkcapi. When performing one-shot symmetric cipher operations on large inputs (over 64 KiB) in stateful modes such as Counter (CTR) or Cipher Block Chaining (CBC), the library improperly reuses the Initialization Vector (IV) for each internal data chunk. A remote attacker could potentially exploit this by making an application that uses libkcapi process specially crafted large inputs. This can lead to a significant weakening of data confidentiality, as the repeated IV use can expose relationships in encrypted plaintext, and may also affect data integrity by causing incorrect cryptographic processing.

A flaw was found in libkcapi. When performing one-shot symmetric cipher operations on large inputs (over 64 KiB) in stateful modes such as Counter (CTR) or Cipher Block Chaining (CBC), the library improperly reuses the Initialization Vector (IV) for each internal data chunk. A remote attacker could potentially exploit this by making an application that uses libkcapi process specially crafted large inputs. This can lead to a significant weakening of data confidentiality, as the repeated IV use can expose relationships in encrypted plaintext, and may also affect data integrity by causing incorrect cryptographic processing.

This issue was discovered by Found by AISLE in partnership with Red Hat. To mitigate this issue, applications using `libkcapi` should avoid the one-shot symmetric cipher APIs for inputs exceeding 64 KiB when continuous-message semantics are critical. Instead, prefer the streaming interface for processing large messages, or ensure one-shot inputs remain below the internal chunking threshold to guarantee the IV is applied consistently throughout the operation. Red Hat Enterprise Linux 10 Affected libkcapi Red Hat Enterprise Linux 8 Affected libkcapi Red Hat Enterprise Linux 9 Affected libkcapi Red Hat Hardened Images Affected libkcapi Red Hat OpenShift Container Platform 4 Fix deferred rhcos https://www.cve.org/CVERecord?id=CVE-2026-71225 https://nvd.nist.gov/vuln/detail/CVE-2026-71225