CVE-2015-6789

CVE: CVE-2015-6789
CWE:
- 362
- 416
bugs:
- 557981
repo: 
vccs:
- note: Added the line declaring a HashSet of raw pointers.
  commit: e15b315960c47d964f9537abbdd2d0f45fe095dd
fixes:
- note: |
    Updated to use reference pointers for MutationObservers rather than raw pointers.
    The reference pointer is a smart pointer introduced in WebKit which allows objects
    essentially change ownership as they move location.  In the case of this vulnerability,
    the reference pointer allowed methods to reference the correct location of the object
    as it moved.
  commit: a17c2c87065be2c4dcb586583b1d69a5c85dae20
bounty:
  date: '2015-12-08 14:56:00.000000000 -05:00'
  amount: 2000.0
  references:
  - http://chromereleases.googleblog.com/2015/12/stable-channel-update_8.html
lessons:
  yagni:
    note: 
    applies: 
  question: |
    Are there any common lessons we have learned from class that apply to this
    vulnerability? In other words, could this vulnerability serve as an example
    of one of those lessons?

    Leave "applies" blank or put false if you did not see that lesson (you do
    not need to put a reason). Put "true" if you feel the lesson applies and put
    a quick explanation of how it applies.

    Don't feel the need to claim that ALL of these apply, but it's pretty likely
    that one or two of them apply.

    If you think of another lesson we covered in class that applies here, feel
    free to give it a small name and add one in the same format as these.
  serial_killer:
    note: 
    applies: 
  complex_inputs:
    note: 
    applies: 
  distrust_input:
    note: 
    applies: 
  least_privilege:
    note: 
    applies: 
  native_wrappers:
    note: 
    applies: 
  defense_in_depth:
    note: 
    applies: 
  secure_by_default:
    note: 
    applies: 
  environment_variables:
    note: 
    applies: 
  security_by_obscurity:
    note: 
    applies: 
  frameworks_are_optional:
    note: 
    applies: 
reviews:
- 1473023006
- 1463433002
- 1495433002
upvotes: 2
mistakes:
  answer: "A developer removed support for specific heap memory testing, which was
    relevant \nas the vulnerability resulted in a heap related error when discovered.
    \ Removal of\nthis support may have resulted in the six month discovery time for
    the vulnerability.\nThis issue may have been discovered with more robust unit
    testing, but only the developer\nwho implemented the fix added testing for the
    MutationObserver HashShet.  Improved testing\nand capability for testing could
    have lead to earlier discovery for this issue.\n"
  question: |
    In your opinion, after all of this research, what mistakes were made that
    led to this vulnerability? Coding mistakes? Design mistakes?
    Maintainability? Requirements? Miscommunications?

    Look at the CWE entry for this vulnerability and examine the mitigations
    they have written there. Are they doing those? Does the fix look proper?

    Use those questions to inspire your answer. Don't feel obligated to answer
    every one. Write a thoughtful entry here that those ing the software
    engineering industry would find interesting.
announced: '2015-12-14 06:59:01.573000000 -05:00'
subsystem:
  name: Blink
  answer: The test case which revealed the vulnerability was testing the Blink subsystem.
  question: |
    What subsystems was the mistake in?

    Look at the path of the source code files code that were fixed to get
    directory names. Look at comments in the code. Look at the bug reports how
    the bug report was tagged. Examples: "clipboard", "gpu", "ssl", "speech", "renderer"
discovered:
  date: 2015-18-11
  answer: |
    The vulnerability was discovered by a user named CloudFuzz.  The user posted
    output from the AddressSanitizer testing tool, which is recommended for bug testing
    by Google.  The posted crash logs show it was from the user's test case, indicating they
    were purposefully testing parts of the program.
  google: false
  contest: false
  question: |
    How was this vulnerability discovered?

    Go to the bug report and read the conversation to find out how this was
    originally found. Answer in longform below in "answer", fill in the date in
    YYYY-MM-DD, and then determine if the vulnerability was found by a Google
    employee (you can tell from their email address). If it's clear that the
    vulenrability was discovered by a contest, fill in the name there.

    The "automated" flag can be true, false, or nil.
    The "google" flag can be true, false, or nil.

    If there is no evidence as to how this vulnerability was found, then you may
    leave the entries blank except for "answer". Write down where you looked in "answer".
  automated: true
description: |
  Blink is an open source rendering engine used to visualize web content loaded by Chrome.
  The affected code uses MutationObserver objects to monitor and log specific events.
  The MutationObserver objects are stored using raw pointers, which cause use-after-free
  issues if the object is no longer at the expected location in memory when the pointer is
  referenced.  Exploiting this vulnerability requires the creation and subsequent deletion
  of a MutationObserver object, which will result in denial-of-service when a crash is caused.
unit_tested:
  fix: true
  code: false
  answer: "The fix commit added unit tests which specifically tested deleting a \nMutationObserver
    while events were collected from it.\n"
  question: |
    Were automated unit tests involved in this vulnerability?
    Was the original code unit tested, or not unit tested? Did the fix involve
    improving the automated tests?

    For the "code" answer below, look not only at the fix but the surrounding
    code near the fix and determine if and was there were unit tests involved
    for this module.

    For the "fix" answer below, check if the fix for the vulnerability involves
    adding or improving an automated test to ensure this doesn't happen again.
major_events:
  answer: "ClusterFuzz is an automated testing tool used extensively in the Chromium
    project.\nIt allows testers to create custom fuzzers for testing.  ClusterFuzz
    interacts with \ndiscussion around reported issues by commenting with results
    as they are discovered.\n"
  events:
  - event:
      date: 2015-19-11
      name: ClusterFuzz tool usage, first comment.
  - event:
      date: 
      name: 
  question: |
    Please record any major events you found in the history of this
    vulnerability. Was the code rewritten at some point? Was a nearby subsystem
    changed? Did the team change?

    The event doesn't need to be directly related to this vulnerability, rather,
    we want to capture what the development team was dealing with at the time.
curation_level: 1
CWE_instructions: |
  Please go to cwe.mitre.org and find the most specific, appropriate CWE entry
  that describes your vulnerability. (Tip: this may not be a good one to start
  with - spend time understanding this vulnerability before making your choice!)
bounty_instructions: |
  If you came across any indications that a bounty was paid out for this
  vulnerability, fill it out here. Or correct it if the information already here
  was wrong. Otherwise, leave it blank.
interesting_commits:
  answer: 
  commits:
  - note: Developer removed support for tracing off-heap hashmaps.
    commit: 33c3f827e80eb301d5fcc6d0fbb23275a3a98f73
  - note: 
    commit: 
  question: |
    Are there any interesting commits between your VCC(s) and fix(es)?

    Write a brief (under 100 words) description of why you think this commit was
    interesting in light of the lessons learned from this vulnerability. Any
    emerging themes?

    If there are no interesting commits, demonstrate that you completed this section by explaining what happened between the VCCs and the fix.
curated_instructions: |
  If you are manually editing this file, then you are "curating" it. Set the
  entry below to "true" as soon as you start. This will enable additional
  integrity checks on this file to make sure you fill everything out properly.
  If you are a student, we cannot accept your work as finished unless curated is
  set to true.
upvotes_instructions: |
  For the first round, ignore this upvotes number.

  For the second round of reviewing, you will be giving a certain amount of
  upvotes to each vulnerability you see. Your peers will tell you how
  interesting they think this vulnerability is, and you'll add that to the
  upvotes score on your branch.
announced_instructions: |
  Was there a date that this vulnerability was announced to the world? You can
  find this in changelogs, blogs, bug reports, or perhaps the CVE date. A good
  source for this is Chrome's Stable Release Channel
  (https://chromereleases.googleblog.com/).
  Please enter your date in YYYY-MM-DD format.
fixes_vcc_instructions: |
  Please put the commit hash in "commit" below (see my example in
  CVE-2011-3092.yml). Fixes and VCCs follow the same format.
description_instructions: |
  You can get an initial description from the CVE entry on cve.mitre.org. These
  descriptions are a fine start, but they can be kind of jargony.

  Rewrite this description in your own words. Make it interesting and easy to
  read to anyone with some programming experience. We can always pull up the NVD
  description later to get more technical.

  Try to still be specific in your description, but remove Chromium-specific
  stuff. Remove references to versions, specific filenames, and other jargon
  that outsiders to Chromium would not understand. Technology like "regular
  expressions" is fine, and security phrases like "invalid write" are fine to
  keep too.