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Bug 1546858 - (CVE-2018-7225) CVE-2018-7225 libvncserver: Improper input sanitization in rfbProcessClientNormalMessage in rfbserver.c
CVE-2018-7225 libvncserver: Improper input sanitization in rfbProcessClientNo...
Status: CLOSED ERRATA
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
medium Severity medium
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Assigned To: Red Hat Product Security
impact=moderate,public=20180218,repor...
: Security
Depends On: 1546859 1546860 1548440 1548441
Blocks: 1546862
  Show dependency tree / graph
 
Reported: 2018-02-19 15:09 EST by Laura Pardo
Modified: 2018-04-11 05:31 EDT (History)
3 users (show)

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Last Closed: 2018-04-11 05:31:21 EDT
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Attachments (Terms of Use)
Proposed fix (2.71 KB, patch)
2018-02-26 08:39 EST, Petr Pisar 		no flags Details | Diff
Proposed fix to mitigate excessive memory use (1.70 KB, patch)
2018-03-06 07:17 EST, Petr Pisar 		no flags Details | Diff
Add an attachment (proposed patch, testcase, etc.)


External Trackers
Tracker ID Priority Status Summary Last Updated
Github LibVNC/libvncserver/issues/218 None None None 2018-02-26 08:36 EST
Red Hat Product Errata RHSA-2018:1055 None None None 2018-04-10 05:10 EDT

  None (edit)
Description Laura Pardo 2018-02-19 15:09:31 EST 
An issue was discovered in LibVNCServer through 0.9.11. rfbProcessClientNormalMessage() in rfbserver.c does not sanitize msg.cct.length, leading to access to uninitialized and potentially sensitive data or possibly unspecified other impact (e.g., an integer overflow) via specially crafted VNC packets.


References:
https://github.com/LibVNC/libvncserver/issues/218
http://www.openwall.com/lists/oss-security/2018/02/18/1
Comment 1 Laura Pardo 2018-02-19 15:10:00 EST 
Created libvncserver tracking bugs for this issue:

Affects: epel-7 [bug 1546859]
Affects: fedora-all [bug 1546860]
Comment 4 Petr Pisar 2018-02-26 08:39 EST 
Created attachment 1400842 [details]
Proposed fix

This prevents from the integer overflow.

However, it does not impose any length limit to prevent from allocating a lot of memory as I don't know what the sane limit should be.
Comment 5 Petr Pisar 2018-03-06 07:17 EST 
Created attachment 1404775 [details]
Proposed fix to mitigate excessive memory use

The original patch fixes only the use of noninicialized memory. This second patch prevents from a DoS when a client request a valid but really big buffer size (2 GB) by limiting the acceptable size to 1 MB.
Comment 7 Fedora Update System 2018-03-27 16:13:05 EDT 
libvncserver-0.9.11-5.fc27 has been pushed to the Fedora 27 stable repository. If problems still persist, please make note of it in this bug report.
Comment 8 Fedora Update System 2018-03-30 09:16:55 EDT 
libvncserver-0.9.11-6.fc28 has been pushed to the Fedora 28 stable repository. If problems still persist, please make note of it in this bug report.
Comment 9 Fedora Update System 2018-04-03 10:24:36 EDT 
libvncserver-0.9.11-3.fc26 has been pushed to the Fedora 26 stable repository. If problems still persist, please make note of it in this bug report.
Comment 10 errata-xmlrpc 2018-04-10 05:10:12 EDT 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2018:1055 https://access.redhat.com/errata/RHSA-2018:1055
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