CVE-2007-3048 : Detail

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

_ _ _____ _ ___ _____ _ _ / / / / ____/ / / _/_ __/ / / / / /_/ / __/ / / / / / / / /_/ / / __ / /___/ /____/ / / / / __ / /_/ /_/_____/_____/___/ /_/ /_/ /_/ Helith - 0815 -------------------------------------------------------------------------------- Author : Rembrandt Date : 2007-06-03 Affected Software: screen <= 4.0.3 Affected OS : OpenBSD up to 4.4 (and propably others) Type : Local Authentication Bypass OSVDB : 39587 Milw0rm : 4028 CVE : 2007-3048 ISS X-Force: : 34693 screen, on some operating systems, is vulnerable to a local terminal screen lock authentication bypass that may allow physically proximate attackers to gain access to the system. This issue has been confirmed on OpenBSD with screen 4.0.3 on x86/amd64. The underlying vulnerability may be related to 3rd party authentication such as PAM. This issue was tested on OpenSuSE with screen 4.0.2 and was not vulnerable. Steps to reproduce: $ screen -S test [Screened session starts] $ id uid=1001(test) gid=1001(test) groups=1001(test) $ [type ctrl-a x] Key: test Again: test Screen used by test <test>. Password: [type ctrl-c] $ screen -r [Regained access to screen, without password] The screen lock mechanism is designed to lock a terminal, not the entire shell session. If an attacker has shell access to the target account, it is understood they can bypass protection. However, on the system tested, the screen lock mechanism was bypassed using 'ctrl-c'. The vulnerability is not in OpenBSD. screen developers indicate this is known behavior, but do not appear to fully understand the scenario with which this can be abused. Replies to my initial disclosure suggest this may be related to PAM authentication, or another 3rd party package. Testing was not performed to fully identify the vulnerable code. Tobias Ulmer has committed a patch to the screen code that prevents this exploit from happening. Kind regards, Rembrandt # milw0rm.com [2008-06-18]