CVE-2021-22901

curl: Use-after-free in TLS session handling when using OpenSSL TLS backend

Published Jun 11, 2021 CVSS 3.1 · 8.1 High EPSS 63.5% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

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History
Weaknesses

Sources

Status
PUBLISHED
Assigner
hackerone
Published
Updated
Oct 14, 2026, 10:31 AM
Reserved
Jan 6, 2021, 12:00 AM
Status
Modified
Published
Jun 11, 2021, 4:15 PM
Modified
Oct 14, 2026, 11:16 AM
Severity
Important
Public date
May 26, 2021, 12:00 AM