PKCS#12 Files with PBMAC1 Are Accepted with Short HMAC Keys

7.4 / 10

HIGH

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

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.

Basic Information

ID CVE-2026-34181

Source openssl

Published Jun 9, 2026 at 16:03

Modified Jun 10, 2026 at 16:02

Affected Product

Vendor OpenSSL

Product OpenSSL

Version 4.0.0

Affected Versions OpenSSL OpenSSL 4.0.0
OpenSSL OpenSSL 3.6.0
OpenSSL OpenSSL 3.5.0
OpenSSL OpenSSL 3.4.0

CWE Classification

CWE-354

References

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    "lastseen": "",
    "description": "Issue Summary: The PKCS#12 file processing fails to perform sufficient input\nvalidation for files that use Password-Based Message Authentication Code 1\n(PBMAC1) integrity mechanism allowing a certificate and private key forgery.\n\nImpact Summary: An attacker impersonating a user can cause a service reading\nPKCS#12 files to accept forged certificates and private keys with a 1 in 256\nprobability.\n\nIf a service accepting PKCS#12 files is using passwords for authenticating\nthe received files, the attacker can create unencrypted PKCS#12 files that\nuse PBMAC1 authentication that specifies an HMAC key of only one byte, allowing\nthem to craft a file that will be accepted with a 1 in 256 probability.\nThat would then cause the service to accept a certificate and private key\ncontrolled by the attacker.\n\nThe FIPS modules are not affected by this issue, as the affected code is\noutside the OpenSSL FIPS module boundary.",
    "published": "2026-06-09T16:03:22.065Z",
    "modified": "2026-06-10T16:02:19.675Z",
    "type": "cve",
    "title": "PKCS#12 Files with PBMAC1 Are Accepted with Short HMAC Keys",
    "source": "openssl",
    "references": "https://openssl-library.org/news/secadv/20260609.txt\nhttps://github.com/openssl/openssl/commit/0300eb9ddce7a0895bf301a4b0c03a9da2313a0f\nhttps://github.com/openssl/openssl/commit/ec36f2417c4ddd8cabce4b4a60a3d7a7365f2d81\nhttps://github.com/openssl/openssl/commit/85dcbb3abaa4878af5c8fbbe11bce708fcf984a7\nhttps://github.com/openssl/openssl/commit/79eb76a937e474bb7610a0a3dc57131dc8dc6610",
    "id": "CVE-2026-34181",
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    "cwe": [
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    "sourceData": "OpenSSL OpenSSL 4.0.0\nOpenSSL OpenSSL 3.6.0\nOpenSSL OpenSSL 3.5.0\nOpenSSL OpenSSL 3.4.0",
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}

PKCS#12 Files with PBMAC1 Are Accepted with Short HMAC Keys_CVE-2026-34181