Vulnerability in OpenSSL
CVE-2026-34181
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.002 (7.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 7.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: -0.001
Affected products
- OpenSSL — versions 4.0.0, 3.6.0, 3.5.0
Weakness classification (CWE)
References
- github.com/openssl/security/commit/0300eb9ddce7a0895bf301a4b0c03a9da2313a0f
- github.com/openssl/security/commit/79eb76a937e474bb7610a0a3dc57131dc8dc6610
- github.com/openssl/security/commit/85dcbb3abaa4878af5c8fbbe11bce708fcf984a7
- github.com/openssl/security/commit/ec36f2417c4ddd8cabce4b4a60a3d7a7365f2d81
- openssl-library.org/news/secadv/20260609.txt (vendor-advisory, Vendor Advisory)
- github.com/openssl/openssl/commit/0300eb9ddce7a0895bf301a4b0c03a9da2313a0f (Patch, patch)
- github.com/openssl/openssl/commit/79eb76a937e474bb7610a0a3dc57131dc8dc6610 (Patch, patch)
- github.com/openssl/openssl/commit/85dcbb3abaa4878af5c8fbbe11bce708fcf984a7 (Patch, patch)
- github.com/openssl/openssl/commit/ec36f2417c4ddd8cabce4b4a60a3d7a7365f2d81 (Patch, patch)
Frequently asked questions
- What is CVE-2026-34181?
- CVE-2026-34181 is a high-severity vulnerability in OpenSSL, classified under Improper Validation of Integrity Check Value. CVSS score: 7.4/10. Published 2026-06-09.
- How severe is CVE-2026-34181?
- High severity. CVSS v3 base score is 7.4 out of 10.