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Fencer Vulns
medium 6.5

CVE-2026-71225 json

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

published 2026-08-05 3 mo ago modified 2026-11-02 7 d ago also EUVD-2026-53336

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

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.

Patch / fix

  • Stephan Muelle libkcapi 1.5.1
  • Red Hat Red Hat Enterprise Linux 10 0:1.5.1-1.el10_2
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support 0:1.5.0-6.el10_0
  • Red Hat Red Hat Enterprise Linux 8 0:1.4.0-3.el8_10
  • Red Hat Red Hat Enterprise Linux 9 0:1.4.0-3.el9_8
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support 0:1.4.0-2.el9_6.1
  • Red Hat Red Hat Hardened Images 1.5.1-0.1.hum1
  • libkcapi Debian 14 1.5.1-1

debian advisories DEBIAN-CVE-2026-71225

  • libkcapi RHEL 8 1.4.0-3.el8_10
  • libkcapi-hmaccalc RHEL 8 1.4.0-3.el8_10
  • libkcapi RHEL 10.2 1.5.1-1.el10_2
  • libkcapi-hasher RHEL 10.2 1.5.1-1.el10_2
  • libkcapi-hmaccalc RHEL 10.2 1.5.1-1.el10_2
  • libkcapi RHEL 9 1.4.0-3.el9_8
  • libkcapi-hmaccalc RHEL 9 1.4.0-3.el9_8
  • libkcapi hummingbird 1 1.5.1-0.1.hum1

red hat advisories RHSA-2026:69285RHSA-2026:67266RHSA-2026:67267RHSA-2026:67265RHSA-2026:56985

  • libkcapi AlmaLinux 9 1.4.0-3.el9_8
  • libkcapi-hmaccalc AlmaLinux 9 1.4.0-3.el9_8
  • libkcapi AlmaLinux 8 1.4.0-3.el8_10
  • libkcapi-hmaccalc AlmaLinux 8 1.4.0-3.el8_10
  • libkcapi AlmaLinux 10 1.5.1-1.el10_2
  • libkcapi-hasher AlmaLinux 10 1.5.1-1.el10_2
  • libkcapi-hmaccalc AlmaLinux 10 1.5.1-1.el10_2

almalinux advisories ALSA-2026:67265ALSA-2026:67266ALSA-2026:67267

  • libkcapi Rocky Linux 9 1.4.0-3.el9_8
  • libkcapi Rocky Linux 10 1.5.1-1.el10_2
  • libkcapi Rocky Linux 8 1.4.0-3.el8_10

rocky linux advisories RLSA-2026:67265RLSA-2026:67267RLSA-2026:67266

  • libkcapi Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 1.5.1-r0

alpine advisories ALPINE-CVE-2026-71225

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libkcapi Azure Linux 3.0 1.5.1-1

azure linux advisories AZL-94655

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-71225 updated cvss 6.5

libkcapi: IV reuse in libkcapi one-shot symmetric cipher chunking causes cipher state reset across chunk boundaries

  • Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux BaseOS (v. 8) libkcapi 1.4.0-3.el8_10, libkcapi-hmaccalc 1.4.0-3.el8_10
    fixed: vendor fix RHSA-2026:67266
  • Red Hat Enterprise Linux BaseOS (v. 9) libkcapi 1.4.0-3.el9_8, libkcapi-hmaccalc 1.4.0-3.el9_8
    fixed: vendor fix RHSA-2026:67265
  • Red Hat Enterprise Linux BaseOS (v. 10) libkcapi 1.5.1-1.el10_2, libkcapi-hasher 1.5.1-1.el10_2, libkcapi-hmaccalc 1.5.1-1.el10_2
    fixed: vendor fix RHSA-2026:67267
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) libkcapi 1.5.0-6.el10_0
    fixed: vendor fix RHSA-2026:69285
  • Red Hat Enterprise Linux BaseOS EUS (v.9.6) libkcapi 1.4.0-2.el9_6.1, libkcapi-hmaccalc 1.4.0-2.el9_6.1
    fixed: vendor fix RHSA-2026:87712
  • Red Hat Hardened Images libkcapi 1.5.1-0.1.hum1, libkcapi-tests 1.5.1-0.1.hum1, libkcapi-tools 1.5.1-0.1.hum1, libkcapi-hasher 1.5.1-0.1.hum1, libkcapi-hmaccalc 1.5.1-0.1.hum1, libkcapi-fipscheck 1.5.1-0.1.hum1
    fixed: vendor fix RHSA-2026:56985
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) libkcapi-hasher 1.5.0-6.el10_0, libkcapi-hmaccalc 1.5.0-6.el10_0 Red Hat Enterprise Linux BaseOS EUS (v.9.6) libkcapi-tests-debuginfo 1.4.0-2.el9_6.1, libkcapi-tools-debuginfo 1.4.0-2.el9_6.1, libkcapi-hmaccalc-debuginfo 1.4.0-2.el9_6.1, libkcapi-fipscheck-debuginfo 1.4.0-2.el9_6.1
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugzilla.redhat.com https://bugzilla.redhat.com/show_bug.cgi?id=2462011 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N

Affected products

  • Stephan Muelle libkcapi
  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support
  • Red Hat Red Hat Hardened Images
  • Red Hat Red Hat OpenShift Container Platform 4
  • Red Hat Red Hat OpenShift Container Platform 5

Classification

Weakness
  • CWE-330 Use of Insufficiently Random Values

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.