Bug 1561953 (CVE-2018-8778)

Summary: CVE-2018-8778 ruby: Buffer under-read in String#unpack
Product: [Other] Security Response Reporter: Adam Mariš <amaris>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: bkearney, cbillett, cbuissar, ccoleman, cpelland, dajohnso, dedgar, dmcphers, gblomqui, hhorak, hhudgeon, jaruga, jgoulding, jorton, jprause, mtasaka, pvalena, ruby-maint, s, strzibny, tomckay, vanmeeuwen+fedora, vondruch
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: ruby 2.2.10, ruby 2.3.7, ruby 2.4.4, ruby 2.5.1 Doc Type: If docs needed, set a value
Doc Text:
A integer underflow was found in the way String#unpack decodes the unpacking format. An attacker, able to control the unpack format, could use this flaw to disclose arbitrary parts of the application's memory.
Story Points: ---
Clone Of: Environment:
Last Closed: 2019-06-10 10:19:18 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1561956, 1561957, 1561958, 1563869, 1563870, 1563871, 1563872, 1563873, 1563874, 1565258, 1566580, 1566581, 1566582, 1566583, 1566584, 1651798, 1652037, 1652038, 1802767, 1802769, 1821481    
Bug Blocks: 1561954    

Description Adam Mariš 2018-03-29 09:09:13 UTC
String#unpack receives format specifiers as its parameter, and can be specified the position of parsing the data by the specifier @. If a big number is passed with @, the number is treated as the negative value, and out-of-buffer read is occurred. So, if a script accepts an external input as the argument of String#unpack, the attacker can read data on heaps.

Affected versions:

Ruby 2.2 series: 2.2.9 and earlier
Ruby 2.3 series: 2.3.6 and earlier
Ruby 2.4 series: 2.4.3 and earlier
Ruby 2.5 series: 2.5.0 and earlier

External References:

https://www.ruby-lang.org/en/news/2018/03/28/buffer-under-read-unpack-cve-2018-8778/

Comment 1 Adam Mariš 2018-03-29 09:15:42 UTC
Created ruby tracking bugs for this issue:

Affects: fedora-all [bug 1561957]

Comment 11 Cedric Buissart 2018-04-12 08:13:00 UTC
Mitigation:

Vulnerable code when String#unpack's argument is attacker controlled.
In the unpack format string argemument, manual sanitization can be done by preventing the number following '@' to overflow to a negative number. See https://dev.to/sqreenio/an-in-depth-look-at-cve-2018-8878-or-why-integer-overflows-are-still-a-thing-1n01 for mitigation details.

Comment 13 Cedric Buissart 2018-04-13 08:31:41 UTC
Upstream fix : 
https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=62992

Comment 14 Andrej Nemec 2018-05-14 15:26:15 UTC
Statement:

This issue affects the versions of ruby as shipped with Red Hat CloudForms 4. Red Hat Product Security has rated this issue as having security impact of Moderate. A future update may address this issue. For additional information, refer to the Issue Severity Classification: https://access.redhat.com/security/updates/classification/.

This issue affects the versions of ruby as shipped with Red Hat Subscription Asset Manager 1. Red Hat Product Security has rated this issue as having security impact of Moderate. A future update may address this issue. For additional information, refer to the Issue Severity Classification: https://access.redhat.com/security/updates/classification/.

Comment 20 errata-xmlrpc 2018-11-29 09:57:00 UTC
This issue has been addressed in the following products:

  Red Hat Software Collections for Red Hat Enterprise Linux 6
  Red Hat Software Collections for Red Hat Enterprise Linux 7
  Red Hat Software Collections for Red Hat Enterprise Linux 7.4 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7.5 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7.6 EUS

Via RHSA-2018:3729 https://access.redhat.com/errata/RHSA-2018:3729

Comment 21 errata-xmlrpc 2018-11-29 10:11:39 UTC
This issue has been addressed in the following products:

  Red Hat Software Collections for Red Hat Enterprise Linux 6
  Red Hat Software Collections for Red Hat Enterprise Linux 7
  Red Hat Software Collections for Red Hat Enterprise Linux 7.4 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7.5 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7.6 EUS

Via RHSA-2018:3730 https://access.redhat.com/errata/RHSA-2018:3730

Comment 22 errata-xmlrpc 2018-11-29 10:22:51 UTC
This issue has been addressed in the following products:

  Red Hat Software Collections for Red Hat Enterprise Linux 7
  Red Hat Software Collections for Red Hat Enterprise Linux 7.4 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7.5 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7.6 EUS

Via RHSA-2018:3731 https://access.redhat.com/errata/RHSA-2018:3731

Comment 23 errata-xmlrpc 2019-08-06 12:03:55 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2019:2028 https://access.redhat.com/errata/RHSA-2019:2028

Comment 27 errata-xmlrpc 2020-04-29 10:06:51 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7.5 Extended Update Support

Via RHSA-2020:1963 https://access.redhat.com/errata/RHSA-2020:1963

Comment 28 errata-xmlrpc 2020-05-19 14:41:07 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7.4 Advanced Update Support
  Red Hat Enterprise Linux 7.4 Update Services for SAP Solutions
  Red Hat Enterprise Linux 7.4 Telco Extended Update Support

Via RHSA-2020:2212 https://access.redhat.com/errata/RHSA-2020:2212

Comment 29 errata-xmlrpc 2020-05-26 11:16:54 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7.6 Extended Update Support

Via RHSA-2020:2288 https://access.redhat.com/errata/RHSA-2020:2288