CVE-2026-71225 in Red Hat
Summary
by MITRE • 08/05/2026
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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Analysis
by VulDB Data Team • 08/05/2026
The vulnerability in libkcapi represents a critical cryptographic flaw that undermines the security guarantees of symmetric encryption operations when processing large data inputs exceeding 64 KiB. This issue specifically affects stateful cipher modes including Counter (CTR) and Cipher Block Chaining (CBC) where the library fails to properly manage Initialization Vector (IV) usage across multiple internal processing chunks. The improper IV reuse occurs during one-shot operations that split large inputs into smaller segments for processing, creating a fundamental weakness in the cryptographic implementation that directly violates established security principles.
The technical flaw stems from the library's failure to increment or properly derive new IV values for each subsequent data chunk when operating on large inputs. In proper cryptographic implementations, each encryption operation within a stateful mode should utilize a unique IV to maintain confidentiality guarantees and prevent pattern recognition attacks. The CWE-329 weakness classification applies here as the vulnerability directly involves improper generation and reuse of initialization vectors in cryptographic operations. This flaw allows attackers to potentially perform statistical analysis on encrypted data streams, as repeated IV usage in CTR mode creates predictable keystream patterns that can be exploited through known plaintext attacks or differential cryptanalysis techniques.
The operational impact of this vulnerability extends beyond simple confidentiality breaches to encompass potential data integrity compromise within applications relying on libkcapi for cryptographic operations. Remote attackers can craft malicious inputs that trigger the vulnerable code path, causing applications to process data with reused IVs and subsequently weaken encryption strength. The attack surface is particularly concerning for network services or applications processing large files, where the repeated IV exposure could lead to complete decryption of sensitive information or manipulation of encrypted data streams. This vulnerability aligns with ATT&CK technique T1552.004 for unsecured credentials and T1074.001 for data staging through encryption manipulation.
Mitigation strategies should focus on immediate library updates from vendors, as the flaw requires core cryptographic library modifications to properly handle IV management during large input processing. Organizations should implement monitoring for applications using libkcapi to detect potential exploitation attempts, particularly those involving large file transfers or bulk data operations. The recommended approach includes patching to ensure proper IV incrementation or derivation for each internal chunk processing, along with implementing application-level checks to validate input sizes that could trigger the vulnerable code path. Additionally, system administrators should consider temporary workarounds such as limiting input sizes processed through affected libraries or deploying cryptographic modules with proper IV management implementations to prevent exploitation while permanent fixes are implemented.