# CVE-2026-40253

> Vulnerability · severity: **MEDIUM** (CVSS 6.8).

## Description

openCryptoki is a PKCS#11 library and provides tooling for Linux and AIX. In versions 3.26.0 and below, the BER/DER decoding functions in the shared common library (asn1.c) accept a raw pointer but no buffer length parameter, and trust attacker-controlled BER length fields without validating them against actual buffer boundaries. All primitive decoders are affected: ber_decode_INTEGER, ber_decode_SEQUENCE, ber_decode_OCTET_STRING, ber_decode_BIT_STRING, and ber_decode_CHOICE. Additionally, ber_decode_INTEGER can produce integer underflows when the encoded length is zero. An attacker supplying a malformed BER-encoded cryptographic object through PKCS#11 operations such as C_CreateObject or C_UnwrapKey, token loading from disk, or remote backend communication can trigger out-of-bounds reads. This affects all token backends (Soft, ICA, CCA, TPM, EP11, ICSF) since the vulnerable code is in the shared common library. A patch is available thorugh commit ed378f463ef73364c89feb0fc923f4dc867332a3.

## Key facts

- **CVE ID:** CVE-2026-40253
- **Published:** 2026-04-16
- **CVSS severity:** MEDIUM
- **CVSS base score:** 6.8
- **CWE codes:** CWE-125

## Affected products

- `opencryptoki_project:opencryptoki`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40253

## Citation

> AI Analytics. CVE-2026-40253. Retrieved 2026-07-15 from https://api.ai-analytics.org/cve/CVE-2026-40253. Derived from NIST NVD. Licensed CC0.

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