Signature Detail

HTTP: Lighttpd url-path-2f-decode Denial of Service

This signature detects attempts to exploit a known vulnerability against Lighttpd. This vulnerability is due to improper handling of URL when url-path-2f-decode is enabled. A remote, unauthenticated attacker can exploit this vulnerability by sending a maliciously crafted HTTP request to the target server. Successful exploitation of this vulnerability could result in denial-of-service condition on the target server.

Extended Description

** DISPUTED ** lighttpd before 1.4.54 has a signed integer overflow, which might allow remote attackers to cause a denial of service (application crash) or possibly have unspecified other impact via a malicious HTTP GET request, as demonstrated by mishandling of /%2F? in burl_normalize_2F_to_slash_fix in burl.c. NOTE: The developer states "The feature which can be abused to cause the crash is a new feature in lighttpd 1.4.50, and is not enabled by default. It must be explicitly configured in the config file (e.g. lighttpd.conf). Certain input will trigger an abort() in lighttpd when that feature is enabled. lighttpd detects the underflow or realloc() will fail (in both 32-bit and 64-bit executables), also detected in lighttpd. Either triggers an explicit abort() by lighttpd. This is not exploitable beyond triggering the explicit abort() with subsequent application exit."

Affected Products

• Lighttpd lighttpd 1.4.53

References

• CVE: CVE-2019-11072