A recently discovered bug in the GnuTLS cryptographic code library puts users of Linux and hundreds of other open source packages at risk of surreptitious malware attacks until they incorporate a fix developers quietly pushed out late last week.
Maliciously configured servers can exploit the bug by sending malformed data to devices as they establish encrypted HTTPS connections. Devices that rely on an unpatched version of GnuTLS can then be remotely hijacked by malicious code of the attacker's choosing, security researchers who examined the fix warned. The bug wasn't patched until Friday, with the release of GnuTLS versions 3.1.25, 3.2.15, and 3.3.4. While the patch has been available for three days, it will protect people only when the GnuTLS-dependent software they use has incorporated it. With
literally hundreds of packages dependent on the library multiple operating systems dependent on the library, that may take time.
"A flaw was found in the way GnuTLS parsed session IDs from ServerHello messages of the TLS/SSL handshake," an entry posted Monday on the Red Hat Bug Tracker explained. "A malicious server could use this flaw to send an excessively long session ID value, which would trigger a buffer overflow in a connecting TLS/SSL client application using GnuTLS, causing the client application to crash or possibly execute arbitrary code."