CVE-2026-42768
Description
A flaw was found in OpenSSL's CMS_decrypt() and PKCS7_decrypt() functions. This vulnerability, a Bleichenbacher-style oracle, could allow a remote attacker to decrypt or sign messages using the victim's private RSA key. Exploitation requires the attacker to provide specially crafted CMS or S/MIME messages and observe the application's error codes or decryption output. While the attack is technically possible, the specific conditions required make it unlikely to be exploited in typical deployments.
Statement
This Low severity vulnerability in OpenSSL's CMS_decrypt() and PKCS7_decrypt() functions exposes a Bleichenbacher-style oracle. Exploitation requires an attacker to control input CMS/S/MIME messages and observe decryption errors or output, a scenario deemed unlikely in most Red Hat product deployments. The attack could allow decryption or signing of messages with a victim's private RSA key.
Mitigation
To mitigate this vulnerability, applications utilizing CMS_decrypt() or PKCS7_decrypt() should ensure a recipient certificate is always provided to identify the specific RecipientInfo for decryption. This practice helps prevent the Bleichenbacher-style oracle attack by ensuring proper key identification.
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 | 6.3 | N/A | 3.7 |
| Attack Vector | Local | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | Low | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | Low |
| Integrity Impact | High | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Understanding the Weakness (CWE)
Confidentiality,Access Control
Technical Impact: Read Application Data; Bypass Protection Mechanism
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