CVE-2026-21898 is an out-of-bounds read vulnerability classified under CWE-125 found in NASA's CryptoLib, a software-only implementation of the CCSDS Space Data Link Security Protocol - Extended Procedures (SDLS-EP). This protocol secures communication between spacecraft running the core Flight System (cFS) and ground stations. The vulnerability resides in the Crypto_AOS_ProcessSecurity function, which processes AOS (Advanced Orbiting Systems) frame hashes. Prior to version 1.4.3, this function reads memory without proper bounds checking, potentially accessing memory beyond allocated buffers. Such out-of-bounds reads can cause application crashes leading to denial of service (availability impact) or may leak sensitive information from adjacent memory areas (confidentiality impact). The vulnerability is remotely exploitable over the network without requiring authentication or user interaction, increasing its risk profile. Although no exploits are currently known in the wild, the flaw poses a significant threat to systems relying on CryptoLib for secure spacecraft communication. The issue was addressed by NASA in version 1.4.3 by implementing proper bounds checking during hash parsing. This vulnerability highlights the criticality of rigorous input validation in security protocol implementations, especially in aerospace contexts where communication integrity and availability are paramount.

For European organizations, particularly those involved in aerospace, satellite communications, or space research collaborating with NASA or using CCSDS protocols, this vulnerability could disrupt secure communication channels between spacecraft and ground stations. A successful exploitation could cause denial of service by crashing the CryptoLib component, potentially interrupting mission-critical data flows. Additionally, there is a risk of sensitive data leakage from memory, which could compromise confidentiality of mission data or cryptographic material. Given the specialized nature of the software, the impact is mostly confined to aerospace and space agencies, but any European entity relying on these protocols or software stacks could face operational disruptions and data exposure. The availability impact could delay mission operations or ground control responses, while confidentiality breaches could undermine trust and security of space communication infrastructure.

The primary mitigation is to upgrade all instances of NASA's CryptoLib to version 1.4.3 or later, where the out-of-bounds read issue has been patched. Organizations should conduct an inventory of systems using CryptoLib, especially those handling spacecraft communication, to identify vulnerable versions. Implement rigorous input validation and memory safety checks in any custom or derivative implementations of the SDLS-EP protocol. Employ runtime protections such as memory-safe languages or bounds-checking tools where feasible. Monitor network traffic for anomalous AOS frame hashes that could indicate exploitation attempts. Coordinate with NASA and aerospace partners to ensure timely patch deployment and share threat intelligence. Finally, conduct regular security assessments and fuzz testing on protocol parsers to detect similar vulnerabilities proactively.