CVE-2026-34181 is a high-severity (CVSS 7.4) CWE-354 vulnerability. A fix is available — see the affected versions and patch details below.
PKCS#12 Files with PBMAC1 Are Accepted with Short HMAC Keys
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34181.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-34181 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 380,526 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Description
Issue Summary: The PKCS#12 file processing fails to perform sufficient input validation for files that use Password-Based Message Authentication Code 1 (PBMAC1) integrity mechanism allowing a certificate and private key forgery.
Impact Summary: An attacker impersonating a user can cause a service reading PKCS#12 files to accept forged certificates and private keys with a 1 in 256 probability.
If a service accepting PKCS#12 files is using passwords for authenticating the received files, the attacker can create unencrypted PKCS#12 files that use PBMAC1 authentication that specifies an HMAC key of only one byte, allowing them to craft a file that will be accepted with a 1 in 256 probability. That would then cause the service to accept a certificate and private key controlled by the attacker.
The FIPS modules are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.
Affected Products
opensslopensslDetection & mitigation playbook
VulnerabilityDetect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Fix
Upgrade the affected component to the fixed release for CVE-2026-34181, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Low: This flaw allows an attacker to forge PKCS#12 files with a 1 in 256 probability, leading to the acceptance of attacker-controlled certificates and private keys by services configured to use PBMAC1 authentication. Red Hat products utilizing OpenSSL versions 3.0, 1.1.1, or 1.0.2 are not affected, as these versions…
To mitigate this issue, enforce strict validation on all uploaded PKCS#12 files to reject those containing abnormally short security keys. Additionally, enabling FIPS mode on your system can help protect your environment, as the vulnerable OpenSSL code operates entirely outside the approved FIPS cryptographic boundary.Source: Red Hat security advisory for CVE-2026-34181 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 10 | openssl-1:3.5.5-4.el10_2 | RHSA-2026:25237 |
| Red Hat Enterprise Linux 9 | openssl-1:3.5.5-4.el9_8 | RHSA-2026:25239 |
| Cert Manager support for Red Hat OpenShift release 1.20 | cert-manager/cert-manager-trust-manager-rhel9:1790598593 | RHSA-2026:72502 |
| Red Hat Discovery 2 | discovery/discovery-server-rhel9:1782159791 | RHSA-2026:29197 |
| Red Hat Hardened Images | chunkah-main-0.6.0-3.hum1 | RHSA-2026:42825 |
| Red Hat Hardened Images | python-cryptography-main-50.0.0-1.hum1 | RHSA-2026:55543 |
| Red Hat Hardened Images | openssl3-main-3.5.8-0.1.hum1 | RHSA-2026:59635 |
| Red Hat Hardened Images | openssl-main-3.5.8-0.1.hum1 | RHSA-2026:59641 |
Frequently Asked Questions
Is CVE-2026-34181 in your dependencies?
Find it across , including transitive dependencies.