Observable discrepancy in OpenSSL - CVE-2026-42768

Vulnerability identifier: #VU134283

CSH Severity: Medium

CVSS v4: 9.1 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-42768

CWE-ID: CWE-203

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to decrypt or sign messages with the victim's private RSA key.

The vulnerability exists due to observable discrepancy in error handling in CMS_decrypt() and PKCS7_decrypt() when processing attacker-supplied CMS or S/MIME messages and exposing decryption errors or output differences. A remote attacker can send crafted messages and observe the application's responses to decrypt or sign messages with the victim's private RSA key.

The attack requires the application to expose the error code and/or decryption output in a way that can be observed by the attacker.

OpenSSL
Debian Linux
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
Fedora
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for x86_64
FreeBSD
Basesystem Module
openEuler
Ubuntu
IBM Cloud Pak for Data System
IBM MQ Operator
LANTIME Operating System Firmware (LTOS)
IBM supplied MQ Advanced container images
Operator for PostgreSQL
EntireX
openssl (Ubuntu package)
openssl (Debian package)
openssl-3-debugsource
libopenssl-3-fips-provider-32bit
libopenssl3-32bit
libopenssl-3-fips-provider-32bit-debuginfo
libopenssl3-32bit-debuginfo
openssl-3
libopenssl-3-fips-provider-debuginfo
openssl-3-debuginfo
libopenssl3
libopenssl-3-devel
libopenssl3-debuginfo
libopenssl-3-fips-provider
openssl (Red Hat package)
openssl3
openssl
edk2-ovmf
python3-edk2-devel
edk2-help
edk2-aarch64
edk2-devel
edk2-debugsource
edk2-debuginfo
edk2

Install security update from vendor's website.

OpenSSL - addressed in versions 3.4.6, 3.5.7, 3.6.3, 4.0.1
IBM Cloud Pak for Data System - update to 8.10.26.07.SP3
IBM MQ Operator - addressed in versions 3.2.26 SC2, 4.0.1 SC2
LANTIME Operating System Firmware (LTOS) - update to 7.10.013
IBM supplied MQ Advanced container images - update to 10.0.0.0-r2
EntireX - update to 12.1 Fix2
openssl (Ubuntu package) - addressed in versions 3.0.2-0ubuntu1.25, 3.0.13-0ubuntu3.11, 3.5.3-1ubuntu3.4, 3.5.5-1ubuntu3.2
openssl (Debian package) - addressed in versions 3.0.20-1~deb12u2, 3.5.6-1~deb13u2
openssl-3-debugsource - update to 3.2.3-150700.5.36.1
libopenssl-3-fips-provider-32bit - update to 3.2.3-150700.5.36.1
libopenssl3-32bit - update to 3.2.3-150700.5.36.1
libopenssl-3-fips-provider-32bit-debuginfo - update to 3.2.3-150700.5.36.1
libopenssl3-32bit-debuginfo - update to 3.2.3-150700.5.36.1
openssl-3 - update to 3.2.3-150700.5.36.1
libopenssl-3-fips-provider-debuginfo - update to 3.2.3-150700.5.36.1
openssl-3-debuginfo - update to 3.2.3-150700.5.36.1
libopenssl3 - update to 3.2.3-150700.5.36.1
libopenssl-3-devel - update to 3.2.3-150700.5.36.1
libopenssl3-debuginfo - update to 3.2.3-150700.5.36.1
libopenssl-3-fips-provider - update to 3.2.3-150700.5.36.1
openssl (Red Hat package) - addressed in versions 3.5.5-4.el9_8, 3.5.5-4.el10_2
openssl3 - update to 3.5.5-5.el8
openssl - update to 3.5.7-1.fc44
edk2-ovmf - addressed in versions 202002-38, 202011-36, 202308-41, 202308-45
python3-edk2-devel - addressed in versions 202002-38, 202011-36, 202308-41, 202308-45
edk2-help - addressed in versions 202002-38, 202011-36, 202308-41, 202308-45
edk2-aarch64 - addressed in versions 202002-38, 202011-36, 202308-41, 202308-45
edk2-devel - addressed in versions 202002-38, 202011-36, 202308-41, 202308-45
edk2-debugsource - addressed in versions 202002-38, 202011-36, 202308-41, 202308-45
edk2-debuginfo - addressed in versions 202002-38, 202011-36, 202308-41, 202308-45
edk2 - addressed in versions 202002-38, 202011-36, 202308-41, 202308-45

• https://openssl-library.org/news/secadv/20260609.txt

• Multiple vulnerabilities in OpenSSL
• Debian update for openssl
• Ubuntu update for openssl
• Fedora 44 update for openssl
• Red Hat Enterprise Linux 10 update for openssl
• Red Hat Enterprise Linux 9 update for openssl
• FreeBSd update for OpenSSL
• SUSE update for openssl-3
• Multiple vulnerabilities in IBM Operator for PostgreSQL
• Multiple vulnerabilities in IBM EntireX
• Multiple vulnerabilities in IBM MQ Operator and Queue manager container images
• openEuler 24.03 LTS SP1 update for edk2
• openEuler 22.03 LTS SP4 update for edk2
• openEuler 20.03 LTS SP4 update for edk2
• openEuler 24.03 LTS SP4 update for edk2
• openEuler 24.03 LTS SP3 update for edk2
• Fedora EPEL 8 update for openssl3
• Multiple vulnerabilities in Meinberg LANTIME firmware
• Multiple vulnerabilities in IBM Cloud Pak for Data System