CVE-2026-71225
Received Received - Intake

Heap-Based Buffer Overflow in libkcapi Cryptographic Library

Publication date: 2026-08-05

Last updated on: 2026-08-05

Assigner: Red Hat, Inc.

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.

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Meta Information

Published
2026-08-05
Last Modified
2026-08-05
Generated
2026-08-05
AI Q&A
2026-08-05
EPSS Evaluated
N/A
NVD
CVE-2026-71225
EUVD
EUVD-2026-53336

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
red_hat libkcapi 1.5.0-3.el10

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-330 The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.

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Executive Summary

This vulnerability affects libkcapi when processing large inputs over 64 KiB in stateful cipher modes like CTR or CBC. The library incorrectly reuses the Initialization Vector (IV) for each internal data chunk, breaking continuous-message behavior. This weakens data confidentiality by exposing plaintext relationships and may affect integrity due to incorrect cryptographic processing.

Detection Guidance

To detect this vulnerability, check if your system uses libkcapi version 1.5.0-3.el10 or affected versions. Inspect applications using one-shot symmetric cipher APIs for large inputs (>64 KiB) in CTR or CBC modes. Look for repeated IV reuse across chunk boundaries in ciphertext patterns.

Impact Analysis

If you use an affected application relying on libkcapi for large data encryption or decryption, an attacker could exploit this flaw by sending specially crafted inputs. This may lead to weakened confidentiality (e.g., plaintext recovery) or incorrect decryption results, depending on the cipher mode and application behavior.

Compliance Impact

This vulnerability could impact compliance by weakening data confidentiality, which is critical under GDPR and HIPAA. Repeated IV reuse may expose sensitive data, violating requirements for strong encryption and data protection. Affected systems may fail audits or require remediation to restore compliance.

Mitigation Strategies

Avoid using one-shot symmetric cipher APIs for large inputs (>64 KiB) in CTR or CBC modes. Switch to streaming interfaces for large messages. Ensure one-shot inputs remain below the internal chunking threshold. Monitor for patches and upgrade to fixed versions when available.

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