OpenSSL Addresses 'HollowByte' DoS Vulnerability with Silent Fixes
A vulnerability in OpenSSL, known as 'HollowByte', has been identified, allowing attackers to exhaust a server's memory before any security handshake. Discovered by Okta's red team, the denial-of-service (DoS) bug can be triggered by a malicious payload of only 11 bytes, which declares a larger incoming message body to initiate a buffer pre-allocation that is not immediately freed. This vulnerability existed because older OpenSSL versions pre-allocated receive buffer sizes based on the incoming message body length declared in the handshake message's 4-byte header. The issue has been silently fixed in OpenSSL version 4.0.1 and backported to earlier versions. 
