CVE-2025-37984 addresses a vulnerability in the Linux kernel's cryptographic subsystem, specifically within the ECDSA (Elliptic Curve Digital Signature Algorithm) implementation. The issue arises from the use of the DIV_ROUND_UP() macro, which performs division with rounding up but can cause integer overflows when the input value is unusually large. The vulnerability is linked to the ->key_size() callback function in the ECDSA implementation, which may return unexpectedly large values. Such overflows can lead to incorrect calculations in cryptographic operations, potentially resulting in memory corruption or logic errors. The fix involves introducing a safer macro, DIV_ROUND_UP_POW2(), which uses a formula (X / 8 + !!(X & 7)) that prevents unnecessary overflows during division by powers of two. This macro replaces the original DIV_ROUND_UP() in key size calculations and is also applied in the ecc_digits_from_bytes() function, which processes key sizes or ASN.1 lengths for signature components. Although no known exploits are currently reported in the wild, the vulnerability could theoretically be exploited to cause denial of service or compromise cryptographic integrity if an attacker can influence the key size parameters. The vulnerability affects specific Linux kernel versions identified by commit hashes, and the patch was published in May 2025.

For European organizations, the impact of this vulnerability depends largely on their use of Linux-based systems that perform ECDSA cryptographic operations, such as servers, network devices, or embedded systems. If exploited, the integer overflow could lead to memory corruption, potentially causing system crashes or enabling attackers to bypass cryptographic protections. This could undermine the confidentiality and integrity of sensitive data, disrupt critical services, or facilitate further attacks. Organizations relying on Linux kernels with vulnerable versions in critical infrastructure, financial services, healthcare, or government sectors may face increased risk. The absence of known exploits reduces immediate threat levels, but the cryptographic nature of the flaw means that any exploitation could have severe consequences for secure communications and data protection. Additionally, the complexity of exploitation and requirement for unusual key sizes may limit the scope, but targeted attacks against high-value assets remain a concern.

European organizations should promptly update their Linux kernel versions to incorporate the patch that replaces DIV_ROUND_UP() with the safer DIV_ROUND_UP_POW2() macro. Kernel maintainers and system administrators must verify that their systems are running patched versions corresponding to the commit hashes referenced. For environments where immediate patching is challenging, organizations should audit cryptographic configurations to ensure that key sizes are within expected ranges and not user-controllable in a manner that could trigger the overflow. Implementing strict input validation on cryptographic parameters and monitoring for anomalous kernel behavior or crashes related to ECDSA operations can provide additional defense. Security teams should also review cryptographic libraries and dependent applications for indirect exposure and consider deploying runtime protections such as kernel memory protection mechanisms and address space layout randomization (ASLR) to mitigate exploitation impact. Finally, maintaining up-to-date threat intelligence and vulnerability management processes will help detect any emerging exploits targeting this vulnerability.