CVE-2021-22901

curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session ticket arrives over a connection. A malicious server can use this in rare unfortunate circumstances to potentially reach remote code execution in the client. When libcurl at run-time sets up support for TLS 1.3 session tickets on a connection using OpenSSL, it stores pointers to the transfer in-memory object for later retrieval when a session ticket arrives. If the connection is used by multiple transfers (like with a reused HTTP/1.1 connection or multiplexed HTTP/2 connection) that first transfer object might be freed before the new session is established on that connection and then the function will access a memory buffer that might be freed. When using that memory, libcurl might even call a function pointer in the object, making it possible for a remote code execution if the server could somehow manage to get crafted memory content into the correct place in memory.

• CWE-416
• CWE-416

• https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdfPatch, Third Party Advisory
• https://cert-portal.siemens.com/productcert/pdf/ssa-732250.pdfThird Party Advisory
• https://curl.se/docs/CVE-2021-22901.htmlExploit, Patch, Vendor Advisory
• https://github.com/curl/curl/commit/7f4a9a9b2a49547eae24d2e19bc5c346e9026479Patch, Third Party Advisory
• https://hackerone.com/reports/1180380Exploit, Issue Tracking, Third Party Advisory
• https://security.netapp.com/advisory/ntap-20210723-0001/Third Party Advisory
• https://security.netapp.com/advisory/ntap-20210727-0007/Third Party Advisory
• https://www.oracle.com//security-alerts/cpujul2021.htmlPatch, Third Party Advisory
• https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
• https://www.oracle.com/security-alerts/cpujan2022.htmlPatch, Third Party Advisory
• https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdfPatch, Third Party Advisory
• https://cert-portal.siemens.com/productcert/pdf/ssa-732250.pdfThird Party Advisory
• https://curl.se/docs/CVE-2021-22901.htmlExploit, Patch, Vendor Advisory
• https://github.com/curl/curl/commit/7f4a9a9b2a49547eae24d2e19bc5c346e9026479Patch, Third Party Advisory
• https://hackerone.com/reports/1180380Exploit, Issue Tracking, Third Party Advisory
• https://security.netapp.com/advisory/ntap-20210723-0001/Third Party Advisory
• https://security.netapp.com/advisory/ntap-20210727-0007/Third Party Advisory
• https://www.oracle.com//security-alerts/cpujul2021.htmlPatch, Third Party Advisory
• https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
• https://www.oracle.com/security-alerts/cpujan2022.htmlPatch, Third Party Advisory

Published

Jun 11, 2021

Last Modified

Jun 17, 2026

Status

Modified

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