CVE-2016-5127

CVE: CVE-2016-5127
CWE:
- 416
bugs:
- 618237
- 622566
repo: 
vccs:
- note: There was a function called isEditablePosition().This function was called
    with a parameter called DoUpdateStyle. It was used to decide whether or not the
    layout tree would need updating. The thing is a function called previousLinePosition()
    updates the layout tree at entry. However, despite there being an initial call
    to preiousLinePosition(), there may still be pending style sheets. If the attacker
    uses the rel=import attribute of a LINK element to try and import a file, the
    style sheet will be considered pending since the document isn't rendering ready.
    Therefore the layout tree will be updated, regardless of the state of DoUpdateStyle.
  commit: fb81c66590538c2487a34b8623066a22d0b27dff
- note: This was a fix for MSAN. MSAN is MemorySanitizer (MSan). It is a tool that
    detects the use of uninitialized memory. The pending style sheet is memory that
    the attacker can attack.
  commit: 2217e8c563575ead5c9450408529340ec93ccef7
fixes:
- note: ''
  commit: e9c943f368d15bbfe414aedf5e001792257f3eeb
- note: 
  commit: c1b06954220f96a85ce764396cf5cc5e24a9fba4
- note: ''
  commit: f60b4eb00abc12a1fa2575890f7c77b373a1bedc
- note: ''
  commit: fb81c66590538c2487a34b8623066a22d0b27dff
bounty:
  date: '2016-07-20 '
  amount: 3000.0
  references:
  - http://chromereleases.googleblog.com/2016/07/stable-channel-update.html
lessons:
  yagni:
    note: 
    applies: false
  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: false
  complex_inputs:
    note: 
    applies: false
  distrust_input:
    note: 
    applies: false
  least_privilege:
    note: "This applies. Attackers were given privileges they shouldn't have had due
      to the \nability they had to access the CSS and HTML.\n"
    applies: true
  native_wrappers:
    note: 
    applies: false
  defense_in_depth:
    note: 
    applies: false
  secure_by_default:
    note: 
    applies: false
  environment_variables:
    note: 
    applies: false
  security_by_obscurity:
    note: 
    applies: false
  frameworks_are_optional:
    note: 
    applies: false
reviews:
- 2149913003
- 2082893005
- 2091633002
- 2151143002
- 2084913005
upvotes: 
mistakes:
  answer: "This vulnerability was caused due to a lack of design. The developers did
    not\ndesign the updating of the layout tree appropriately.\n\nCWE-416 is \"Use
    After Free\" weakness. This is when someone references memory\nafter it has been
    freed, causing the program to crash. Presumably, the pending\nfiles is the free
    memory in this scenario. The mitigation to this was to \nset free pointers to
    null after freeing the pointer. In this situation the \nmain fix was making that
    intial check previousLinePosition() to not use dangling \nRootInlineBox. This
    ensures that the memory will no longer be free and vulnerable.\n\nThe developers
    seem to have done a fairly good job at patching the issue quickly and\neffectively.\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: '2016-07-23 '
subsystem:
  name: webkit
  answer: The location of this is based on the location of the problem code.
  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: '2016-06-22'
  answer: "As stated in the previous answer, the research done online would lead one
    to \nbelieve that the bug was intially noticed through some sort of automated
    testing. \nIt appears that it was discovered using something called a ClusterFuzz.
    ClusterFuzz \nis a type of fuzzer. It is used to find vulnerabilities related
    to \nsecurity/stability.\n"
  google: true
  contest: 
  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: "This was a vulnerability that allowed remote attackers to attack Google
  Chrome \nbefore version 52.0.2743.82 had been released. Remote attackers can cause
  a \ndenial of service or possibly other problems that are not specified. \n\nThe
  attacks can be done using JavaScript code. The code involves @import \nat-rule in
  a CSS token sequence along with a rel=import attribute of a \nLINK element. This
  just means that the attacker is able to attack the HTML\nfile while the user is
  trying to import a file. This seems similar to the \nCross-Site Scripting (XSS)
  vulnerability we discussed in class.\n"
unit_tested:
  fix: true
  code: true
  answer: "After googling the CVE, it appears that the bug was found from automated
    tests. \nIt is unclear whether or not the code was intially unit tested. Nobody
    was really\ntalking about that, and there doesn't seem to be any commits related
    to it either.\nThe commit e9c943f368d15bbfe414aedf5e001792257f3eeb has some unit
    tests post fix \nto see if the fix actually worked.\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: 'Did not see any major events occuring at the time of  this time.

    '
  events:
  - date: 
    name: 
  - 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: There were two commits that seemed interesting.
  commits:
  - note: "Update v8 to its newest version. This happened on the same day as the vulnerability
      was found. \nFrom personal experience, updating aspects of the project may lead
      to cause problems in other \naspects of the project.\n"
    commit: f791fc5aab4fd9a3c984591c366edc9f1a0145a1
  - note: "They were working on a fix for something else at the time. However, it
      the \nisEditablePosition() function was changed which may have an affect on
      the vulnerability.\n"
    commit: 33a3a50a0d70c0e701a93c4875d50cd36c5b759f
  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.