OpenSSL Fixes High-Severity DTLS Flaw That Can Leak Heap Memory Unencrypted

OpenSSL has released updates addressing a High-severity vulnerability, CVE-2026-84782, found in its DTLS implementation. The bug can occur when a retransmission timer fires while a large handshake message is still being sent in pieces, causing the resend to grab the wrong buffer position—this can expose unencrypted heap data to the remote peer or crash the application by reading into unmapped memory. There is no indication the flaw has been exploited, and no workaround exists for systems that cannot immediately upgrade. The fix is included in OpenSSL versions 4.0.3, 3.6.5, 3.5.9, and 3.4.8, while patches for the older 3.0, 1.1.1, and 1.0.2 branches are available only through paid premium support, since 3.0 lost public security updates on September 7. CISA scored the issue 8.2 out of 10, and Linux distributions including Ubuntu and Debian have already shipped their own updated packages. The same release batch also resolves 13 lower-severity issues, among them a Moderate flaw (CVE-2026-84783) that could crash multi-threaded TLS clients or servers under specific certificate-chain conditions.