{"id":"CVE-2021-3711","published":"2021-08-24T14:50:13Z","modified":"2026-10-08T21:03:25Z","title":"SM2 Decryption Buffer Overflow","vendor":"OpenSSL","product":"OpenSSL","tier":"core","eol":null,"affectedVersions":[{"vendor":"OpenSSL","product":"OpenSSL","versions":["Fixed in OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k)"]}],"description":{"text":"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).","provenance":"source","from":"CVE.org"},"summary":{"text":"The flaw is a heap buffer overflow in OpenSSL's SM2 decryption code, reached through the EVP_PKEY_decrypt() API, where the size calculated for the first call can be smaller than what the second call needs. An attacker who can get an application to decrypt attacker-supplied SM2 content can overflow the caller's buffer by up to 62 bytes, which can alter adjacent data or crash the application, depending on how the application allocates and uses that buffer.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-29T07:22:46Z"},"cvss":null,"epss":{"score":0.87816,"percentile":0.9976,"date":"2026-10-29","provenance":"source"},"kev":null,"vulncheckKev":null,"exploited":false,"otx":{"pulseCount":3,"pulses":[{"name":"ACTUALIZACION | IBM Watson Speech Services Cartridge for IBM Cloud Pak for Data is vulnerable to multiple Base OS issues","url":"https://otx.alienvault.com/pulse/65e4a6299cb7d09fdd69681a","created":"2024-03-03"},{"name":"ACTUALIZACION | IBM Cognos Analytics has addressed multiple vulnerabilities","url":"https://otx.alienvault.com/pulse/65da2e10a6bc9c007c0c0e32","created":"2024-02-24"},{"name":"Oracle Critical Patch Update Advisory - April 2022","url":"https://otx.alienvault.com/pulse/626040216e00cd388b1b9180","created":"2022-04-20"}],"provenance":"machine"},"cwes":[],"references":[{"url":"https://www.openssl.org/news/secadv/20210824.txt","tags":[]},{"url":"https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=59f5e75f3bced8fc0e130d72a3f582cf7b480b46","tags":[]},{"url":"https://www.debian.org/security/2021/dsa-4963","tags":["vendor-advisory"]},{"url":"https://lists.apache.org/thread.html/r18995de860f0e63635f3008fd2a6aca82394249476d21691e7c59c9e%40%3Cdev.tomcat.apache.org%3E","tags":["mailing-list"]},{"url":"http://www.openwall.com/lists/oss-security/2021/08/26/2","tags":["mailing-list"]},{"url":"https://lists.apache.org/thread.html/rad5d9f83f0d11fb3f8bb148d179b8a9ad7c6a17f18d70e5805a713d1%40%3Cdev.tomcat.apache.org%3E","tags":["mailing-list"]},{"url":"https://security.netapp.com/advisory/ntap-20210827-0010/","tags":[]},{"url":"https://www.oracle.com/security-alerts/cpuoct2021.html","tags":[]},{"url":"https://www.tenable.com/security/tns-2021-16","tags":[]},{"url":"https://www.oracle.com/security-alerts/cpujan2022.html","tags":[]},{"url":"https://security.netapp.com/advisory/ntap-20211022-0003/","tags":[]},{"url":"https://www.tenable.com/security/tns-2022-02","tags":[]},{"url":"https://www.oracle.com/security-alerts/cpuapr2022.html","tags":[]},{"url":"https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf","tags":[]},{"url":"https://security.gentoo.org/glsa/202209-02","tags":["vendor-advisory"]},{"url":"https://security.gentoo.org/glsa/202210-02","tags":["vendor-advisory"]},{"url":"https://security.netapp.com/advisory/ntap-20240621-0006/","tags":[]}],"techniques":[],"reports":[],"affected":[{"ecosystem":"crates.io","package":"openssl-src","vulnerableRanges":["<111.16.0",">=0.0.0-0, <111.16.0"],"patched":["111.16.0"],"from":["GHSA-5ww6-px42-wc85","RUSTSEC-2021-0097"],"provenance":"source"}],"advisories":[{"id":"GHSA-5ww6-px42-wc85","url":"https://github.com/advisories/GHSA-5ww6-px42-wc85","severity":"CRITICAL","ecosystem":"crates.io","package":"openssl-src","vulnerableRanges":["<111.16.0"],"patched":["111.16.0"],"provenance":"source","from":"GHSA"}],"euvd":{"id":"EUVD-2022-2673","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2022-2673","exploited":false,"exploitedSince":null,"provenance":"source"},"exploits":[],"exploitSources":null,"exploitRefs":[],"flow":[],"timeline":[{"date":"2021-08-24","kind":"published","label":"Published (CVE.org)","url":"https://www.cve.org/CVERecord?id=CVE-2021-3711","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":null,"daysToKev":null},"priority":{"score":21.3,"factors":[{"name":"In a KEV catalog","points":0.0,"detail":"not listed"},{"name":"Recent KEV listing","points":0.0,"detail":"not listed"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":19.95,"detail":"percentile 0.9976"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":0.0,"detail":"none found"},{"name":"Mentioned in OTX pulses","points":1.37,"detail":"3 pulses"},{"name":"CVSS severity","points":0.0,"detail":"no CVSS"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]}}