Bug 1484838 - (CVE-2017-12933) CVE-2017-12933 php: buffer over-read in finish_nested_data function
CVE-2017-12933 php: buffer over-read in finish_nested_data function
Status: NEW
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
low Severity low
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Assigned To: Red Hat Product Security
impact=low,public=20170216,reported=2...
: Security
Depends On: 1484840 1554537
Blocks:
  Show dependency treegraph
 
Reported: 2017-08-24 07:59 EDT by Adam Mariš
Modified: 2018-05-03 01:08 EDT (History)
5 users (show)

See Also:
Fixed In Version: php 7.0.21, php 7.1.7
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External Trackers
Tracker ID Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2018:1296 None None None 2018-05-03 01:08 EDT

  None (edit)
Description Adam Mariš 2017-08-24 07:59:06 EDT
The finish_nested_data function in ext/standard/var_unserializer.re in
PHP before 5.6.31, 7.0.x before 7.0.21, and 7.1.x before 7.1.7 is prone
to a buffer over-read while unserializing untrusted data. Exploitation
of this issue can have an unspecified impact on the integrity of PHP.

Upstream bug:

https://bugs.php.net/bug.php?id=74111
Comment 1 Adam Mariš 2017-08-24 08:00:24 EDT
Created php tracking bugs for this issue:

Affects: fedora-all [bug 1484840]
Comment 2 Adam Mariš 2017-08-24 08:04:29 EDT
This issue happens when untrusted input is deserialized. Doing so is documented as being unsafe:

http://php.net/manual/en/function.unserialize.php

"Do not pass untrusted user input to unserialize() regardless of the options value of allowed_classes. Unserialization can result in code being loaded and executed due to object instantiation and autoloading, and a malicious user may be able to exploit this. Use a safe, standard data interchange format such as JSON (via json_decode() and json_encode()) if you need to pass serialized data to the user."

"If you need to unserialize externally stored serialized data, consider to use hash_hmac() for data validation. Make sure data is not modified by anyone, but you."
Comment 4 errata-xmlrpc 2018-05-03 01:08:14 EDT
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 6.7 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7
  Red Hat Software Collections for Red Hat Enterprise Linux 7.3 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7.4 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7.5 EUS

Via RHSA-2018:1296 https://access.redhat.com/errata/RHSA-2018:1296

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