The bug is an out‑of‑bounds read and write in the PKCS#11 Trusted Application of OP‑TEE, originating from missing bounds checks in the function `entry_get_attribute_value()` in `ta/pkcs11/src/object.c`. The flaw permits a malicious client to supply a malformed attribute template that causes the TA to read up to seven bytes beyond the end of the template buffer and then to copy those extra bytes back into the template buffer. This can expose sensitive data stored within the Trusted Execution Environment or corrupt the TA’s memory, potentially leading to a crash.

Affected versions are OP‑TEE OS 3.13.0 through 4.10.0. The vulnerability was fixed by commits e031c4e5, 16926d5a, and 149e8d7e, which are expected to appear in release 4.11.0. All built OP‑TEE images that include the PKCS#11 TA in this version range are impacted, regardless of vendor or deployment.

The CVSS score is 8.7, and the EPSS score is below 1 % with no listing in the CISA KEV catalog. An attacker must be able to invoke the PKCS#11 interface on the TEE; a crafted command using `PKCS11_CMD_GET_ATTRIBUTE_VALUE` is sufficient to exploit the overflow. Because the read/write is limited to a handful of bytes, exploitation may be subtle, but the data revealed can be highly confidential. The risk is therefore high for confidentiality and availability, and the low EPSS implies that exploitation is currently unlikely but still possible, especially in environments that expose the PKCS#11 API widely.