Lighttpd is a lightweight HTTP web server.
Stefan Esser discovered errors with evidence of memory corruption in the code parsing the headers. Several independent researchers also reported errors involving the handling of HTTP headers, the mod_auth and mod_scgi modules, and the limitation of active connections.
A remote attacker can trigger any of these vulnerabilities by sending malicious data to the server, which may lead to a crash or memory exhaustion, and potentially the execution of arbitrary code. Additionally, access-deny settings can be evaded by appending a final / to a URL.
There is no known workaround at this time.
All Lighttpd users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=www-servers/lighttpd-1.4.16"