CVE-2026-79954 in CryptoLib
Summary
by MITRE • 09/18/2026
NASA CryptoLib 1.5.0 contains an authentication downgrade vulnerability in the Telecommand (TC) receive path. The receiver selects the Security Association used for SDLS processing solely from the SPI field inside the incoming frame, but it does not verify that the selected SA is authorized for the frame's GVCID.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified within NASA CryptoLib version 1.5.0 represents a critical authentication downgrade flaw located in the Telecommand receive path of satellite communication systems. This component is responsible for processing incoming security data link service (SDLS) frames, which are essential for secure command and control operations in space missions. The core technical deficiency lies in how the receiver determines which Security Association to utilize for decryption and integrity verification. Specifically, the implementation relies exclusively on the Security Parameter Index field contained within the header of an incoming frame to select the corresponding Security Association from its local database. This approach assumes that the SPI value is sufficient to uniquely identify a valid and authorized security context without further validation against other parameters present in the transmission protocol.
The operational impact of this design flaw stems directly from the lack of cross-verification between the selected Security Association and the Ground Vehicle Channel Identifier associated with the frame. In standard SDLS protocols, both the SPI and GVCID are critical identifiers that must align to ensure that a message is not only cryptographically valid but also authorized for the specific ground vehicle or subsystem it targets. By ignoring the GVCID during SA selection, an attacker can potentially manipulate the incoming traffic to force the receiver into using a Security Association intended for a different context or one with weaker security properties. This misalignment allows for authentication downgrade attacks where the integrity and confidentiality guarantees expected by the system are effectively bypassed because the wrong key material is applied to the data stream.
From a threat modeling perspective, this vulnerability aligns closely with CWE-287, which describes Improper Authentication, as well as CWE-613, Insufficient Session Expiration, in contexts where session parameters are not rigorously validated against their intended scope. Furthermore, it maps to MITRE ATT&CK technique T1550, specifically sub-technique T1550.2, which involves using Alternate Authentication Credentials or manipulating authentication mechanisms to gain unauthorized access. The ability to select an arbitrary Security Association based solely on a single field creates an opportunity for adversaries to exploit trust relationships within the satellite network architecture, potentially leading to command injection or data exfiltration if the downgraded association lacks proper integrity checks.
Mitigation strategies must focus on implementing strict validation logic that ensures consistency between all relevant security parameters before processing any incoming frame. The receiver should verify that the Security Association selected via the SPI is explicitly authorized for the specific GVCID present in the same frame header. This dual-verification process prevents an attacker from leveraging a valid but misappropriated key to decrypt or forge messages intended for other entities within the network. Additionally, implementing strict input validation and logging mechanisms can help detect anomalous patterns where SPI-GVCID mappings deviate from established baselines, providing early warning indicators of potential exploitation attempts in operational environments.