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CVE-2026-34181— PKCS#12 Files with PBMAC1 Are Accepted with Short HMAC Keys

Quick assessment

Affected
OpenSSL OpenSSL
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

OpenSSL是OpenSSL团队的一个开源的能够实现安全套接层（SSLv2/v3）和安全传输层（TLSv1）协议的通用加密库。该产品支持多种加密算法，包括对称密码、哈希算法、安全散列算法等。 OpenSSL存在安全漏洞，该漏洞源于PKCS#12文件处理对使用PBMAC1完整性机制的文件输入验证不足，可能导致证书和私钥伪造，攻击者以1/256概率使服务接受伪造证书和私钥。

AI Predicted 7.5 Difficulty: Easy EPSS 0.18% · P7

Possible ATT&CK Techniques 1 AI

T1556.006 · Multi-Factor Authentication

Affected Version Matrix 4

VendorProduct Version RangeStatus
OpenSSL OpenSSL 4.0.0< 4.0.1 affected
3.6.0< 3.6.3 affected
3.5.0< 3.5.7 affected
3.4.0< 3.4.6 affected
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I. Basic Information for CVE-2026-34181

Vulnerability Information
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Vulnerability Title
PKCS#12 Files with PBMAC1 Are Accepted with Short HMAC Keys
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
完整性检查值验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
OpenSSL 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
OpenSSL是OpenSSL团队的一个开源的能够实现安全套接层（SSLv2/v3）和安全传输层（TLSv1）协议的通用加密库。该产品支持多种加密算法，包括对称密码、哈希算法、安全散列算法等。 OpenSSL存在安全漏洞，该漏洞源于PKCS#12文件处理对使用PBMAC1完整性机制的文件输入验证不足，可能导致证书和私钥伪造，攻击者以1/256概率使服务接受伪造证书和私钥。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
OpenSSL OpenSSL 4.0.0 ~ 4.0.1 -

II. Public POCs for CVE-2026-34181

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III. Intelligence Information for CVE-2026-34181

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Patches & Fixes for CVE-2026-34181 (4)

Vendor Advisories for CVE-2026-34181 (1)

Same Patch Batch · OpenSSL · 2026-06-09 · 18 CVEs total

CVE-2026-45447 Heap Use-After-Free in the PKCS7_verify() Function
CVE-2026-34183 Unbounded Memory Growth in the QUIC PATH_CHALLENGE Handler
CVE-2026-34180 Heap Buffer Over-read in ASN.1 Content Parsing
CVE-2026-34182 CMS AuthEnvelopedData Processing May Accept Forged Messages
CVE-2026-9076 Out-of-Bounds Read in CMS Password-Based Decryption
CVE-2026-35188 Double-free When Checking OCSP Stapled Response
CVE-2026-7383 Possible Heap Buffer Overflow in ASN.1 Multibyte String Conversion
CVE-2026-45446 Incorrect Tag Processing for Empty Messages in AES-GCM-SIV and AES-SIV modes
CVE-2026-45445 AES-OCB IV Ignored on EVP_Cipher() Path
CVE-2026-42771 Possible Out of Bounds Read in X509_VERIFY_PARAM_set1_email()
CVE-2026-42768 Multi-RecipientInfo Bleichenbacher Oracle in CMS_decrypt() and PKCS7_decrypt()
CVE-2026-42769 Trust-Anchor Substitution via cert/issuer Typo in CMP rootCaKeyUpdate
CVE-2026-42767 NULL Pointer Dereference in CRMF EncryptedValue Decryption
CVE-2026-42766 Possible NULL Dereference in Password-Based CMS Decryption
CVE-2026-42764 NULL Pointer Dereference in QUIC Server Initial Packet Handling
CVE-2026-42770 FFC-DH Peer Validation Uses Attacker-Supplied q
CVE-2026-42765 NULL Dereference in Certificate Verification with OCSP Checking

IV. Related Vulnerabilities

Same product: OpenSSL
Same vendor: OpenSSL
Same weakness: CWE-354

V. Comments for CVE-2026-34181

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