CVE-2026-34181

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 v3.1 Score

7.4

HIGH

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS — Exploit Prediction

0.0020

Probability of exploitation

0.09%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-354 CWE-354

Affected Products

Vendor	Product	Versions
openssl	openssl	3.4.0 — 3.4.6
openssl	openssl	3.5.0 — 3.5.7
openssl	openssl	3.6.0 — 3.6.3
openssl	openssl	All

References

Advisories & Patches

https://github.com/openssl/openssl/commit/0300eb9ddce7a0895bf301a4b0c03a9da2313a0f https://github.com/openssl/openssl/commit/79eb76a937e474bb7610a0a3dc57131dc8dc6610 https://github.com/openssl/openssl/commit/85dcbb3abaa4878af5c8fbbe11bce708fcf984a7 https://github.com/openssl/openssl/commit/ec36f2417c4ddd8cabce4b4a60a3d7a7365f2d81 https://openssl-library.org/news/secadv/20260609.txt

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 7.4 (HIGH).

How severe is CVE-2026-34181? +

CVE-2026-34181 has a CVSS v3.1 score of 7.4 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0020, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-34181? +

CVE-2026-34181 affects products from openssl, specifically: openssl. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-34181? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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