High severity · published Jun 9, 2026
CVE-2026-34181
PKCS#12 Files with PBMAC1 Are Accepted with Short HMAC Keys
7.4
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 31% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
OP
OpenSSL · OpenSSL
4.0.0 before 4.0.1; 3.6.0 before 3.6.3; 3.5.0 before 3.5.7; 3.4.0 before 3.4.6 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-34181
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-34181
Patch
https://github.com/openssl/openssl/commit/0300eb9ddce7a0895bf301a4b0c03a9da2313a0f
Patch
https://github.com/openssl/openssl/commit/79eb76a937e474bb7610a0a3dc57131dc8dc6610
Patch
https://github.com/openssl/openssl/commit/85dcbb3abaa4878af5c8fbbe11bce708fcf984a7
Patch
https://github.com/openssl/openssl/commit/ec36f2417c4ddd8cabce4b4a60a3d7a7365f2d81
Vendor Advisory
https://openssl-library.org/news/secadv/20260609.txt
More from OpenSSL
7.5
CVE-2014-0160
OpenSSL Information Disclosure Vulnerability
9.8
CVE-2026-63073
Untrusted Sender DN Used as Format String in CMP Response Validation
9.8
CVE-2026-31789
Heap Buffer Overflow in Hexadecimal Conversion
9.8
CVE-2022-2274
RSA implementation bug in AVX512IFMA instructions
9.8
CVE-2021-3711
SM2 Decryption Buffer Overflow
