CVE-2026-81019 in wolfProvider
Summary
by MITRE • 08/28/2026
wolfProvider before 1.2.2 generates the 8-byte explicit AES-GCM nonce once when the TLS write key is set and never increments it per record. As a result every TLS 1.2 and DTLS 1.2 AES-GCM record within a connection is encrypted under an identical key and nonce pair. Reusing a GCM key and nonce discloses the keystream (the XOR of two ciphertexts equals the XOR of their plaintexts, so one known record recovers the others) and leaks the GHASH authentication key, enabling authentication tag forgery. AES-CCM, TLS 1.3, and non-TLS use of the cipher are not affected.
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Analysis
by VulDB Data Team • 08/28/2026
The vulnerability identified in wolfProvider versions prior to 1.2.2 represents a critical cryptographic implementation flaw within the Transport Layer Security protocol handling logic. Specifically, the library fails to adhere to the fundamental security requirements for AES-GCM mode operation during TLS and DTLS record encryption. In standard secure communications using Galois/Counter Mode, it is imperative that each encrypted record utilizes a unique nonce combined with the same symmetric key. This uniqueness ensures that the keystream generated by the cipher remains distinct for every message, thereby preserving confidentiality and integrity. However, in this affected version of wolfProvider, the eight-byte explicit AES-GCM nonce is initialized only once when the TLS write key is established at the beginning of a connection session. The implementation erroneously retains this single nonce value throughout the entire duration of the connection rather than incrementing or deriving new nonces for subsequent records as mandated by RFC 5288 and RFC 6094 standards governing AES-GCM usage in TLS environments.
This persistent reuse of an identical key and nonce pair fundamentally breaks the security guarantees provided by authenticated encryption with associated data. The primary consequence is a catastrophic loss of confidentiality due to keystream reuse. In stream cipher modes like CTR, which underpins AES-GCM's encryption component, reusing a nonce results in the generation of the exact same pseudorandom bitstream for multiple plaintexts. An attacker observing two ciphertexts encrypted with this reused key and nonce can perform a simple XOR operation on them to eliminate the keystream variable. The resulting value is effectively the XOR of the two underlying plaintexts. If an adversary possesses any partial knowledge or predictable structure within one of these messages, such as standard HTTP headers or known protocol fields, they can immediately recover the corresponding portions of the other message and potentially deduce further information through statistical analysis or brute force techniques against the remaining unknown bytes.
Beyond confidentiality breaches, this flaw severely compromises data integrity by leaking the GHASH authentication key used for generating authentication tags in AES-GCM. The mathematical structure of GCM allows an attacker who can observe multiple ciphertext-tag pairs encrypted under the same nonce to derive the hash subkey H derived from the encryption key. Once the GHASH key is exposed, the attacker gains the ability to forge valid authentication tags for arbitrary malicious data without knowing the original symmetric key. This capability enables active man-in-the-middle attacks where an adversary can intercept legitimate traffic, strip or modify payloads, and append a freshly computed but cryptographically valid tag that will be accepted by the receiving party as authentic. Consequently, both confidentiality and integrity protections are nullified, allowing for complete eavesdropping and data manipulation within the compromised TLS or DTLS session.
The operational impact is particularly severe in environments relying on long-lived connections where multiple records are exchanged over time. While short-lived sessions might limit exposure, any connection that persists beyond a single record exchange becomes vulnerable to immediate exploitation by network-level attackers with packet capture capabilities. It is important to note that this vulnerability does not affect all cryptographic configurations within the library. AES-CCM mode remains unaffected because it employs different nonce management rules and mathematical structures that do suffer from similar reuse issues in this specific context. Furthermore, TLS 1.3 connections are immune to this flaw due to their distinct key derivation mechanisms and mandatory use of unique nonces per record as defined by RFC 8446. Non-TLS applications utilizing the cipher outside of this specific protocol stack integration also remain secure provided they implement correct nonce generation logic independently.
To mitigate this vulnerability, organizations must immediately upgrade wolfProvider to version 1.2.2 or any later release where the issue has been resolved through proper implementation of per-record nonce derivation and incrementation algorithms. During the transition period, if upgrading is not feasible, administrators should enforce shorter connection timeouts to minimize the window of exposure for potential keystream reuse attacks. Additionally, deploying network monitoring solutions capable of detecting anomalies in TLS traffic patterns may help identify ongoing exploitation attempts involving repeated nonces or suspicious authentication tag behaviors. This incident underscores the critical importance of rigorous adherence to cryptographic standards and highlights common pitfalls in custom crypto implementations where nonce management is often overlooked despite its foundational role in secure communication protocols. The flaw aligns with CWE-328, which describes the use of a single value for multiple security-critical operations, and maps to MITRE ATT&CK techniques related to credential access and defense evasion through cryptographic abuse.