CVE-2026-40253
Description
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.
Statement
A moderate severity input validation flaw affects openCryptoki, the PKCS#11 (Cryptographic Token Interface Standard) implementation shipped in Red Hat Enterprise Linux. The BER/DER decoding functions in openCryptoki's shared common library (asn1.c) accept a raw pointer without a buffer length parameter and trust attacker-controlled BER length fields without validating them against the actual buffer boundaries. An attacker who can supply a malformed BER-encoded cryptographic object, for example through PKCS#11 operations such as C_CreateObject or C_UnwrapKey, through loading of a crafted token object from disk, or via remote backend communication, can trigger out-of-bounds reads and integer underflows, resulting in information disclosure and denial of service. Because the vulnerable code resides in the shared common library, all token backends (Soft, ICA, CCA, TPM, EP11, ICSF) are affected. The flaw is rated Moderate severity (CVSS 3.1 score 6.8, AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H), matching the upstream and CVEORG assessments; the NVD score (6.1) differs only marginally and does not change the severity classification. The openCryptoki package in Red Hat Enterprise Linux 6, 7, 8, 9, and 10 is affected: fixes are being pursued for maintained update streams, while the fix is deferred for several older update streams, where the residual risk remains the out-of-bounds read leading to information disclosure and denial of service. The related packages libica, openssl-ibmca, and openssl-ibmpkcs11, and Fedora's opencryptoki package, are not affected because the vulnerable code is not present.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.8 | 6.1 | 6.8 |
| Attack Vector | Local | Local | Local |
| Attack Complexity | Low | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | Required | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | Low | Low | Low |
| Integrity Impact | None | None | None |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
cve.org: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.
Confidentiality
Technical Impact: Bypass Protection Mechanism
Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string.
Other
Technical Impact: Varies by Context
The read operation could produce other undefined or unexpected results.
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