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

Status: published. Published: 2026-08-05. Updated: 2026-11-02.

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.

## Remediation

- workaround: 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. (source: CNA: redhat)

## Affected products and versions

- Stephan Muelle / libkcapi: ≥ 0.10.1; < 1.5.1 (affected, semver). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 10 (libkcapi): ≥ 0:1.5.1-1.el10_2; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 10.0 Extended Update Support (libkcapi): ≥ 0:1.5.0-6.el10_0; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (libkcapi): ≥ 0:1.4.0-3.el8_10; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (libkcapi): ≥ 0:1.4.0-3.el9_8; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9.6 Extended Update Support (libkcapi): ≥ 0:1.4.0-2.el9_6.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Hardened Images (libkcapi-main): ≥ 1.5.1-0.1.hum1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-8): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 5 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 6.5 (medium); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N; source: CNA: redhat

- CISA KEV: No listing in collected sources

- EPSS: 0.34% as of 2026-11-01; percentile 28.12%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-330

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/errata/RHSA-2026:56985 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:67265 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:67266 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:67267 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:69285 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:87712 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-71225 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2462011 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-71225; retrieved 2026-11-02; source updated 2026-11-02

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-71225; retrieved 2026-11-02; source updated Not reported

Revision: 240707fff48232a2253f3c613ffc95b483f4b895c699c5f0a88375e9aa0694c4

Canonical: https://y2.dev/cve/CVE-2026-71225