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CVE-2021-3711— SM2 Decryption Buffer Overflow

Quick assessment

Affected
OpenSSL OpenSSL
Exploitation
High exploitation probability; assess promptly
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 中存在缓冲区错误漏洞，该漏洞源于产品对SM2 plaintext长度的计算错误导致允许越界写操作。攻击者可通过该漏洞执行恶意代码。以下产品及版本受到影响：OpenSSL 1.1.1-1.1.1k。

AI Predicted 8.1 Difficulty: Moderate EPSS 87.82% · P100
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I. Basic Information for CVE-2021-3711

Vulnerability Information
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Vulnerability Title
SM2 Decryption Buffer Overflow
Source: CVE Program / CVE List V5
Vulnerability Description
In order to decrypt SM2 encrypted data an application is expected to call the API function EVP_PKEY_decrypt(). Typically an application will call this function twice. The first time, on entry, the "out" parameter can be NULL and, on exit, the "outlen" parameter is populated with the buffer size required to hold the decrypted plaintext. The application can then allocate a sufficiently sized buffer and call EVP_PKEY_decrypt() again, but this time passing a non-NULL value for the "out" parameter. A bug in the implementation of the SM2 decryption code means that the calculation of the buffer size required to hold the plaintext returned by the first call to EVP_PKEY_decrypt() can be smaller than the actual size required by the second call. This can lead to a buffer overflow when EVP_PKEY_decrypt() is called by the application a second time with a buffer that is too small. A malicious attacker who is able present SM2 content for decryption to an application could cause attacker chosen data to overflow the buffer by up to a maximum of 62 bytes altering the contents of other data held after the buffer, possibly changing application behaviour or causing the application to crash. The location of the buffer is application dependent but is typically heap allocated. Fixed in OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k).
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 缓冲区错误漏洞
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 中存在缓冲区错误漏洞，该漏洞源于产品对SM2 plaintext长度的计算错误导致允许越界写操作。攻击者可通过该漏洞执行恶意代码。以下产品及版本受到影响：OpenSSL 1.1.1-1.1.1k。
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 1.1.1l (Affected 1.1.1-1.1.1k) -

II. Public POCs for CVE-2021-3711

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III. Intelligence Information for CVE-2021-3711

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Vendor Advisories for CVE-2021-3711 (11)

Mailing List Discussions for CVE-2021-3711 (3)

Other References for CVE-2021-3711 (3)

IV. Related Vulnerabilities

Same product: OpenSSL
Same vendor: OpenSSL

V. Comments for CVE-2021-3711

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