CVE-2007-3048 in screen
Summary
by MITRE
** DISPUTED ** GNU screen 4.0.3 allows local users to unlock the screen via a CTRL-C sequence at the password prompt. NOTE: multiple third parties report inability to reproduce this issue.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 01/04/2025
The vulnerability identified as CVE-2007-3048 pertains to GNU screen version 4.0.3, a widely used terminal multiplexer that enables users to manage multiple terminal sessions within a single window. This particular issue relates to the authentication mechanism within GNU screen, specifically concerning how the system handles password prompts and user input sequences. The reported flaw suggests that local attackers may be able to bypass the normal password protection mechanisms through a specific keyboard input sequence involving CTRL-C at the password prompt. This represents a potential privilege escalation vector where unauthorized users could gain access to protected terminal sessions without proper authentication.
The technical nature of this vulnerability aligns with CWE-287, which addresses improper authentication issues in software systems. The flaw demonstrates a weakness in the input handling process during authentication, where the system fails to properly validate or process user input sequences that should be treated as invalid or disruptive to the authentication flow. When a user enters a CTRL-C signal at the password prompt, the system's response mechanism appears to incorrectly interpret this signal as a valid method to bypass the password requirement rather than treating it as an interrupt command that should terminate the authentication process or prompt for re-entry.
From an operational perspective, this vulnerability creates a significant security risk for systems relying on GNU screen for terminal session management and access control. The impact extends beyond simple unauthorized access to potentially compromised session integrity, as attackers could gain access to sensitive terminal sessions, potentially leading to data exposure, privilege escalation, or further system compromise. The local nature of the vulnerability means that an attacker would need physical or account access to the system, but once achieved, the ability to unlock protected sessions without proper authentication represents a serious weakness in the security model.
The disputed nature of this vulnerability, as indicated in the description, reflects the challenges often encountered in security research and vulnerability validation. Multiple third parties reporting inability to reproduce the issue suggests either that the vulnerability may have been incorrectly documented, that specific system configurations are required to trigger the flaw, or that the vulnerability was already addressed in subsequent versions of GNU screen. This uncertainty complicates the assessment of the actual risk level and requires careful consideration of the environment and specific version configurations where such a vulnerability might manifest. Organizations should verify the presence of this issue through proper testing and validation, particularly when dealing with older versions of GNU screen that may have been affected by similar input handling vulnerabilities. The ATT&CK framework would categorize this under privilege escalation techniques, specifically targeting authentication bypass mechanisms where process interruption signals are improperly handled to gain unauthorized access to protected resources.