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

Issue summary: Writing large, newline-free data into a BIO chain using the

line-buffering filter where the next BIO performs short writes can trigger

a heap-based out-of-bounds write.

Impact summary: This out-of-bounds write can cause memory corruption which

typically results in a crash, leading to Denial of Service for an application.

The line-buffering BIO filter (BIO_f_linebuffer) is not used by default in

TLS/SSL data paths. In OpenSSL command-line applications, it is typically

only pushed onto stdout/stderr on VMS systems. Third-party applications that

explicitly use this filter with a BIO chain that can short-write and that

write large, newline-free data influenced by an attacker would be affected.

However, the circumstances where this could happen are unlikely to be under

attacker control, and BIO_f_linebuffer is unlikely to be handling non-curated

data controlled by an attacker. For that reason the issue was assessed as

Low severity.

The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue,

as the BIO implementation is outside the OpenSSL FIPS module boundary.

OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0, 1.1.1 and 1.0.2 are vulnerable to this issue.