CVE-2026-55967 in wolfSSL
Summary
by MITRE • 06/25/2026
AES-GCM encryption/decryption with extremely large cumulative single message sizes (>64 GiB) were not properly rejected by the streaming APIs, allowing counter wrap, keystream reuse, and consequent plaintext recovery.
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Analysis
by VulDB Data Team • 06/25/2026
This vulnerability represents a critical cryptographic flaw in AES-GCM implementations that arises when handling extremely large data volumes exceeding 64 gibibytes within a single message processing operation. The issue stems from the fundamental design limitations of the Galois/Counter Mode algorithm, specifically how it manages the nonce and counter components during streaming encryption and decryption operations. When cumulative message sizes surpass this threshold, the streaming APIs fail to properly validate and reject such operations, creating a dangerous scenario where cryptographic counters can wrap around and repeat keystream values.
The technical root cause lies in the counter overflow handling within the AES-GCM implementation, which should enforce strict limits on message size to prevent the 128-bit counter from wrapping. According to CWE-129, this represents an improper input validation issue where the system fails to check for potentially dangerous parameter values. The vulnerability exploits the mathematical properties of GCM mode where the counter component must remain unique for each encryption operation to maintain security guarantees. When counters wrap around due to excessive data processing, identical keystream segments are generated, enabling attackers to perform differential analysis and recover plaintext information.
The operational impact of this vulnerability extends beyond simple data confidentiality breaches as it fundamentally compromises the integrity of encrypted communications. Attackers who can manipulate or observe the conditions leading to counter wrap can exploit the reused keystream to perform plaintext recovery attacks, particularly effective against ciphertexts with known or predictable content patterns. This weakness aligns with ATT&CK technique T1566 related to credential access through cryptographic attacks and represents a severe degradation of security assurance in systems relying on GCM mode for encryption. The vulnerability affects any system using streaming APIs that process large volumes of data without proper size validation, potentially impacting enterprise security solutions, network protocols, and cryptographic libraries.
Mitigation strategies must address both immediate operational fixes and long-term architectural improvements to prevent similar issues. Systems should implement strict size validation checks at API entry points to reject messages exceeding safe processing limits, typically well below the 64 GiB threshold where counter wrapping becomes problematic. The implementation should include comprehensive input validation mechanisms that enforce message size boundaries before cryptographic operations begin. Organizations must also consider implementing monitoring and alerting for unusual data volume patterns that might indicate attempts to exploit this vulnerability. Additionally, cryptographic libraries should be updated to include robust boundary checking and automatic rejection of dangerous parameter combinations. Security teams should conduct thorough assessments of all streaming encryption implementations and ensure proper testing procedures are in place to validate size limits under various operational conditions.