Copyright © 2012 Red Hat, Inc. All rights reserved. Low 2026-06-09T00:00:00 openssl: OpenSSL: Denial of Service due to heap out-of-bounds read in CMS password-based decryption 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H CWE-131

Issue summary: When CMS password-based decryption (RFC 3211 / PWRI key unwrap) processes attacker-supplied CMS data, an attacker-chosen stream-mode KEK cipher can trigger a heap out-of-bounds read in kek_unwrap_key(). Impact summary: A heap buffer over-read may trigger a crash which leads to Denial of Service for an application if the input buffer ends at a memory page boundary and the following page is unmapped. There is no information disclosure as the over-read bytes are not revealed to the attacker. The key unwrapping function performs a check-byte test as specified in the RFC that reads 7 bytes from a heap allocation that is based on the wrapped key length from the message. There is a minimum length check based on the block length of the wrapping cipher. However the cipher is selected from an OID carried in the attacker's PWRI keyEncryptionAlgorithm with no requirement that the cipher be a block cipher. When an attacker selects a stream-mode cipher the guard will be ineffective and the allocated buffer containing the unwrapped key can be too small to fit the check-bytes specified in the RFC and a buffer over-read can happen. Applications calling CMS_decrypt() or CMS_decrypt_set1_password() (equivalently openssl cms -decrypt -pwri_password ...) on untrusted CMS data are vulnerable to this issue. No password knowledge is required: the over-read happens during the unwrap attempt before any authentication succeeds. The over-read is limited to a few bytes and is not written to output, so there is no information disclosure. Triggering a crash requires the allocation to border unmapped memory, which is unlikely with the normal allocator. The FIPS modules are not affected by this issue.

A flaw was found in OpenSSL. When processing attacker-supplied Cryptographic Message Syntax (CMS) data using password-based decryption, an attacker can choose a stream-mode Key Encryption Key (KEK) cipher. This can trigger a heap out-of-bounds read, potentially causing an application crash and leading to a Denial of Service (DoS). This vulnerability does not require password knowledge and can be exploited before authentication.

This is a Low impact denial of service due to a heap out-of-bounds read in `kek_unwrap_key()` when processing attacker-supplied CMS data with an attacker-chosen stream-mode KEK cipher. This flaw requires specific memory conditions (input buffer ending at a page boundary with an unmapped following page) to trigger a crash, which is uncommon in typical Red Hat environments. No information disclosure is possible, and FIPS modules are not affected. 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. Red Hat Enterprise Linux 10 2026-06-11T00:00:00Z RHSA-2026:25237 openssl-1:3.5.5-4.el10_2 Red Hat Enterprise Linux 9 2026-06-11T00:00:00Z RHSA-2026:25239 openssl-1:3.5.5-4.el9_8 Red Hat Enterprise Linux 9 2026-06-11T00:00:00Z RHSA-2026:25239 openssl-1:3.5.5-4.el9_8 Red Hat Discovery 2 2026-06-24T00:00:00Z RHSA-2026:29197 discovery/discovery-server-rhel9:1782159791 Red Hat Discovery 2 2026-06-24T00:00:00Z RHSA-2026:29197 discovery/discovery-ui-rhel9:1782166952 Red Hat Insights proxy 1.5 2026-07-01T00:00:00Z RHSA-2026:34102 insights-proxy/insights-proxy-container-rhel9:1782890503 Red Hat Update Infrastructure 5 2026-06-16T00:00:00Z RHSA-2026:26319 rhui5/cds-rhel9:1781525684 Red Hat Update Infrastructure 5 2026-06-16T00:00:00Z RHSA-2026:26319 rhui5/haproxy-rhel9:1781525671 Red Hat Update Infrastructure 5 2026-06-16T00:00:00Z RHSA-2026:26319 rhui5/installer-rhel9:1781525693 Red Hat Update Infrastructure 5 2026-06-16T00:00:00Z RHSA-2026:26319 rhui5/rhua-rhel9:1781525739 Red Hat Update Infrastructure 5 2026-08-24T00:00:00Z RHSA-2026:58981 rhui5/cds-kubernetes-tp-rhel9:1787241211 Red Hat Update Infrastructure 5 2026-08-24T00:00:00Z RHSA-2026:58981 rhui5/installer-tp-rhel9:1787135742 Red Hat Update Infrastructure 5 2026-08-24T00:00:00Z RHSA-2026:58981 rhui5/rhua-tp-rhel9:1787241260 Red Hat Enterprise Linux 10 Fix deferred edk2 Red Hat Enterprise Linux 10 Fix deferred shim Red Hat Enterprise Linux 10 Fix deferred shim-unsigned-aarch64 Red Hat Enterprise Linux 10 Fix deferred shim-unsigned-x64 Red Hat Enterprise Linux 6 Fix deferred openssl Red Hat Enterprise Linux 7 Fix deferred ovmf Red Hat Enterprise Linux 8 Fix deferred compat-openssl10 Red Hat Enterprise Linux 8 Fix deferred edk2 Red Hat Enterprise Linux 8 Fix deferred mingw-openssl Red Hat Enterprise Linux 8 Fix deferred openssl Red Hat Enterprise Linux 8 Fix deferred shim Red Hat Enterprise Linux 8 Fix deferred shim-unsigned-x64 Red Hat Enterprise Linux 9 Fix deferred compat-openssl11 Red Hat Enterprise Linux 9 Fix deferred edk2 Red Hat Enterprise Linux 9 Fix deferred shim Red Hat Enterprise Linux 9 Out of support scope shim-unsigned-aarch64 Red Hat Enterprise Linux 9 Fix deferred shim-unsigned-x64 Red Hat JBoss Core Services Not affected jbcs-httpd24-openssl Red Hat JBoss Core Services Not affected jbcs-openssl-win6-x86_64.zip Red Hat JBoss Web Server 6 Not affected jws-optional-native-components-win6-x86_64.zip Red Hat JBoss Web Server 7 Not affected jws-optional-native-components-win6-x86_64.zip Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-9 https://www.cve.org/CVERecord?id=CVE-2026-9076 https://nvd.nist.gov/vuln/detail/CVE-2026-9076