CVE-2026-71225: Libkcapi: iv reuse in libkcapi one-shot symmetric cipher chunking causes cipher state reset across chunk boundaries

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-08-05 · updated 2026-10-22
Weakness: CWE-330

Description

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.

Affected products

Red Hat Enterprise Linux: 8.0, 9.0, 10.0
RedHat Hardened Images: all versions
Red Hat OpenShift Container Platform 4.18: 4.0
smuellerDD Libkcapi: from 0.10.1 before 1.5.1 — fixed in 1.5.1

How to fix

Upgrade to a fixed version: smuellerDD Libkcapi 1.5.1. Check the vendor advisory for mitigations.

References

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