Heap out-of-bounds write in OpenSSL BIO_f_linebuffer on short writes

CVE-2025-68160 is a low-severity memory corruption vulnerability in OpenSSL's line-buffering BIO filter, BIO_f_linebuffer. When large newline-free data is written into a BIO chain using BIO_f_linebuffer and the next BIO in the chain performs short writes, OpenSSL can trigger a heap-based out-of-bounds write. The flaw affects OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0, 1.1.1, and 1.0.2. The issue is outside the OpenSSL FIPS module boundary, so the FIPS modules for 3.6, 3.5, 3.4, 3.3, and 3.0 are not affected. The vulnerable condition is not part of the default TLS/SSL data path; the BIO_f_linebuffer filter is typically only used when applications explicitly add it to a BIO chain, and in OpenSSL command-line applications it is generally only pushed onto stdout/stderr on VMS systems.