Bug 2459076 (CVE-2026-40253)

Summary: CVE-2026-40253 openCryptoki: openCryptoki: Information disclosure and Denial of Service via malformed BER-encoded cryptographic objects
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in openCryptoki, a PKCS#11 (Cryptographic Token Interface Standard) library. The BER/DER (Basic Encoding Rules/Distinguished Encoding Rules) decoding functions in the shared common library do not properly validate attacker-controlled length fields against actual buffer boundaries. This allows an attacker to supply a malformed BER-encoded cryptographic object, potentially through PKCS#11 operations, token loading, or remote backend communication. This can lead to out-of-bounds reads and integer underflows, resulting in information disclosure and a denial of service.
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Description OSIDB Bzimport 2026-04-16 23:01:22 UTC 
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.