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Geo++(R) GNCASTER: Faulty implementation of HTTP Digest Authentication

During a penetration test, RedTeam Pentesting discovered that the GNCaster software has multiple bugs in its implementation of HTTP Digest Authentication.


  • Product: Geo++(R) GNCASTER
  • Affected Versions: <=
  • Fixed Versions:
  • Vulnerability Type: Various types
  • Security Risk: low
  • Vendor URL:
  • Vendor Status: notified
  • Advisory URL:
  • Advisory Status: published
  • CVE: CVE-2010-0551
  • CVE URL:


“Geo++(R) GNCASTER is the Geo++ implementation of a NTRIP caster. NTRIP is a protocol within RTCM to provide GNSS information via Internet.”

(from the vendor’s homepage)

More Details

The authentication method required for requesting the path “/admin.htm” is HTTP Digest. The following flaws were identified during a penetration test:

a) Even though the server states that HTTP Digest is required for authentication, a client can use HTTP Basic Authentication successfully.

b) The server software generates the nonce used for HTTP Digest authentication only once when the server is started. This same nonce is then used for all authentication until the server is restarted. This makes the authentication prone to replay attacks. The nonce is the base64-encoded concatenation of the date and time the server was started and a 16 byte hex string.

c) The server’s response to a failed authentication request contains 32 bytes of data from the service’s memory. This data sometimes contains parts of other users’ HTTP requests. Which portion of memory is disclosed depends on the length of the HTTP request sent. By changing the length of e.g. any request header, attackers might also retrieve the authentication headers sent by other users.




Update GNCASTER to version

Security Risk

Attackers that can record a user’s login communication with the server can replay this authentication information to gain access to the admin interface. Attackers might also be able to gather other users' authentication headers from portions of memory disclosed by the server. However, the admin interface currently does not seem to offer much functionality. Therefore the risk of these vulnerabilities is regarded as low.


  • 2009-07-07 Vulnerability identified during a penetration test
  • 2009-07-14 Meeting with customer
  • 2009-12-01 Vendor releases fixed version
  • 2010-01-27 Advisory released
  • 2011-09-07 CVE information added

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