CVE-2021-3711 Information

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).

CVSS Vector

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

Reference

https://www.openssl.org/news/secadv/20210824.txt https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=59f5e75f3bced8fc0e130d72a3f582cf7b480b46 https://www.debian.org/security/2021/dsa-4963 https://lists.apache.org/thread.html/r18995de860f0e63635f3008fd2a6aca82394249476d21691e7c59c9e@%3Cdev.tomcat.apache.org%3E http://www.openwall.com/lists/oss-security/2021/08/26/2 https://lists.apache.org/thread.html/rad5d9f83f0d11fb3f8bb148d179b8a9ad7c6a17f18d70e5805a713d1@%3Cdev.tomcat.apache.org%3E https://security.netapp.com/advisory/ntap-20210827-0010/ https://www.tenable.com/security/tns-2021-16 https://www.oracle.com/security-alerts/cpuoct2021.html https://security.netapp.com/advisory/ntap-20211022-0003/ https://www.tenable.com/security/tns-2022-02 https://www.oracle.com/security-alerts/cpujan2022.html https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf https://www.oracle.com/security-alerts/cpuapr2022.html

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

9.8