CVE-2025-55398 is a vulnerability identified in the mouse07410 asn1c parser, a fork of the vlm asn1c ASN.1 compiler, specifically affecting versions up to 0.9.29 as of March 20, 2025. The vulnerability arises in the handling of INTEGER constraints during decoding of data encoded using UPER (Unaligned Packed Encoding Rules). UPER is a compact encoding method used in ASN.1 to efficiently serialize data structures for communication protocols. The issue is that the asn1c-generated decoders fail to enforce INTEGER constraints properly when the bound is positive and exceeds 32 bits in length. This means that if an INTEGER value is expected to be within a certain range larger than 32 bits, the decoder does not correctly validate that the input adheres to these constraints. Consequently, this can allow malformed or maliciously crafted input to bypass validation checks and be processed by the application. The failure to enforce these constraints can lead to incorrect data interpretation, potentially causing logic errors, memory corruption, or other undefined behavior depending on how the decoded data is used downstream. Although no known exploits are currently reported in the wild, the vulnerability presents a risk especially in systems relying on ASN.1 UPER encoding for critical communications or data exchange. The lack of a CVSS score indicates that the vulnerability is newly published and has not yet been fully assessed for impact severity. The vulnerability affects the decoding logic within the asn1c-generated code, which is commonly used in telecommunications, embedded systems, and network protocol implementations that rely on ASN.1 specifications for data interchange.

For European organizations, the impact of CVE-2025-55398 could be significant in sectors that utilize ASN.1 UPER encoding for communication protocols, such as telecommunications providers, critical infrastructure operators, and embedded systems manufacturers. Failure to enforce INTEGER constraints can lead to processing of malformed data, potentially resulting in denial of service, data corruption, or escalation of privileges if exploited in conjunction with other vulnerabilities. Telecommunications companies in Europe, which often use ASN.1 for signaling protocols (e.g., 5G, LTE), could face disruptions or security breaches if attackers craft malicious ASN.1 messages exploiting this flaw. Similarly, manufacturers of embedded devices or industrial control systems that rely on ASN.1 for configuration or communication may be at risk of operational failures or security compromises. Although no exploits are currently known, the vulnerability could be leveraged in targeted attacks against critical infrastructure or communication networks, impacting availability and integrity of services. The confidentiality impact is likely lower unless the vulnerability is chained with other flaws to achieve code execution or data leakage. Overall, the vulnerability poses a medium to high risk depending on the deployment context and the criticality of the affected systems within European organizations.

To mitigate CVE-2025-55398, organizations should first identify all systems and applications that use the mouse07410 asn1c parser or its derivatives, especially those handling UPER-encoded ASN.1 data. Since no official patches or updates are currently linked, organizations should monitor the asn1c project repositories and vendor advisories for forthcoming fixes. In the interim, developers should review and enhance the INTEGER constraint validation logic in the ASN.1 decoding routines to ensure that bounds exceeding 32 bits are correctly enforced. This may involve custom validation code or applying stricter input sanitization before processing. Additionally, implementing input fuzzing and static analysis focused on ASN.1 decoding paths can help detect improper constraint enforcement. Network-level mitigations such as filtering or anomaly detection for malformed ASN.1 messages may reduce exposure. For critical systems, consider isolating or sandboxing components that perform ASN.1 decoding to limit potential impact. Finally, organizations should incorporate this vulnerability into their risk management and incident response plans, preparing for potential exploitation scenarios once exploits emerge.