An OpenSC buffer overflow exists in the test_kpgen_certwrite function of pkcs11-tool, allowing an attacker to overflow a buffer during key generation. The flaw can be leveraged remotely, but the high complexity and difficulty of exploitation reduce its practical threat. An attacker who succeeds could corrupt memory or crash the process, potentially leading to denial of service or arbitrary code execution in the worst case.

OpenSC pkcs11-tool versions up to 0.26.1 are impacted. The vulnerability resides within the OpenSC component pkcs11-tool Key Generation Module. The affected product is OpenSC, with the buffer overflow present in the test_kpgen_certwrite routine of pkcs11-tool.c. No later versions than 0.26.1 have been confirmed to contain the fix.

The CVSS score is 2.3, indicating low severity. EPSS data are not available, and the vulnerability is not listed in the CISA KEV catalog. The attack vector is remote, requiring the ability to invoke pkcs11-tool over a network. Exploit complexity is high and exploitability is difficult, yet published proof‑of‑concept code exists, suggesting that skilled adversaries could attempt the exploit. Overall risk remains low but should be mitigated promptly.