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CVE-2021-23841— Null pointer deref in X509_issuer_and_serial_hash()

Quick assessment

Affected
OpenSSL OpenSSL
Exploitation
Public or AI PoC available; prioritize validation
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 public API 存在代码问题漏洞，该漏洞源于 X509_issuer_and_serial_hash 函数不能正确处理解析 issuer 字段时可能发生的任何错误。

AI Predicted 5.5 Difficulty: Moderate EPSS 7.41% · P94

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2021-23841

Vulnerability Information
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Vulnerability Title
Null pointer deref in X509_issuer_and_serial_hash()
Source: CVE Program / CVE List V5
Vulnerability Description
The OpenSSL public API function X509_issuer_and_serial_hash() attempts to create a unique hash value based on the issuer and serial number data contained within an X509 certificate. However it fails to correctly handle any errors that may occur while parsing the issuer field (which might occur if the issuer field is maliciously constructed). This may subsequently result in a NULL pointer deref and a crash leading to a potential denial of service attack. The function X509_issuer_and_serial_hash() is never directly called by OpenSSL itself so applications are only vulnerable if they use this function directly and they use it on certificates that may have been obtained from untrusted sources. OpenSSL versions 1.1.1i and below are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1j. OpenSSL versions 1.0.2x and below are affected by this issue. However OpenSSL 1.0.2 is out of support and no longer receiving public updates. Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2y. Other users should upgrade to 1.1.1j. Fixed in OpenSSL 1.1.1j (Affected 1.1.1-1.1.1i). Fixed in OpenSSL 1.0.2y (Affected 1.0.2-1.0.2x).
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
OpenSSL 代码问题漏洞
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 public API 存在代码问题漏洞，该漏洞源于 X509_issuer_and_serial_hash 函数不能正确处理解析 issuer 字段时可能发生的任何错误。
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 Fixed in OpenSSL 1.1.1j (Affected 1.1.1-1.1.1i) -

II. Public POCs for CVE-2021-23841

# POC Description Source Link Shenlong Link
1 None https://github.com/Trinadh465/external_boringssl_openssl_1.1.0g_CVE-2021-23841 POC Details
2 None https://github.com/Satheesh575555/Openssl_1_1_0_CVE-2021-23841 POC Details
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III. Intelligence Information for CVE-2021-23841

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Vendor Advisories for CVE-2021-23841 (14)

Mailing List Discussions for CVE-2021-23841 (3)

Other References for CVE-2021-23841 (4)

Same Patch Batch · OpenSSL · 2021-02-16 · 3 CVEs total

CVE-2021-23839 Incorrect SSLv2 rollback protection
CVE-2021-23840 Integer overflow in CipherUpdate

IV. Related Vulnerabilities

Same product: OpenSSL
Same vendor: OpenSSL

V. Comments for CVE-2021-23841

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