back to article Chrome's PDF reader has arbitrary code execution flaw

A Researcher at Cisco's Talos limb have discovered an arbitrary code execution flaw in PDFium, the PDF reader installed by default in Google's Chrome browser. CVE-2016-1681, discovered by Talos' Aleksandar Nikolic, means that PDF that includes an embedded jpeg2000 image can trigger an exploitable heap buffer overflow. The …

  1. a_yank_lurker Silver badge

    Keep updated

    Keeping updated is usually highly recommended. Also, setting plugins to not run automatically will help.

  2. Anonymous Coward
    Anonymous Coward

    How many other assertions Chrome removed?

    Was it done as a policy to not compile with assertions enabled? A way to put the dust under the carpet? Assertions are a sort of pre-condition check to ensure code doesn't enter an "unstable" state. Six days to add an IF, hope they also looked for other issues alike...

    1. Adam 52 Silver badge

      Re: How many other assertions Chrome removed?

      Assertions are routinely removed for production builds. They aren't Ada preconditions and they most explicitly are not to prevent code entering an unstable state, they are there to check, during debugging, that it hasn't.

      1. joeldillon

        Re: How many other assertions Chrome removed?

        Note this is not a manual operation. Developers don't go in and comment them out before doing a build or anything. It's standard for assert() to compile to a check if debugging is turned on and to a no-op if it isn't (as is usual for a release build), so it's the compiler doing the removal.

      2. Anonymous Coward
        Anonymous Coward

        Re: How many other assertions Chrome removed?

        No, assertions are not just debug code. They are safety checks. It looks OpenJPEG ships with assertions enabled, but Google decided to disable them.

        In many languages that don't have explicit pre-/post-condition statements, assertions are often used to emulate them, and get out of an execution path that could become dangerous - as in this case - invoking an exception handler so the error can be recorded.

        A simple if () return; may not be enough. There's still an issue, but that has been hidden. What else could go wrong in the same execution path, which may still continue?

        There are production build that removes them, other that leave them exactly as a last line of defense against unexpected situations.

        I'm not worried about the errors and exceptions I see. I'm much more worried about those who gets hidden and I can't see. As in this case.

  3. jake Silver badge

    The whole PDF thing has been ...

    ... a clusterfuck from the year dot.

    Why do people still insist on using the hideously awful concept?

    1. Anonymous Coward
      Anonymous Coward

      Re: The whole PDF thing has been ...

      "Why do people still insist on using the hideously awful concept?"

      What is hideously awful about the concept of PDFs?

      What is hideously awful is the feature creep in Word resulting in truly terrible documents put out by people who think they are designers. A program to produce print-ready files has an obvious use case. A program that tries to combine the functions of a manual typewriter with a whole load of desk top publishing add ons is not.

  4. G2

    NO, Google has NOT fixed the flaw for all Chrome users.

    WinXP users, even if they use the POSReady patches that will be provided by Microsoft until 2019, are still stuck at Chrome v49.0.2623.112

    Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.112 Safari/537.36

    this is the LAST EVER Chrome version that Google published for WinXP... and it's affected by this [potentially-remote] code execution bug. There are NO back-ports of any fixes from v50+ to the Chrome v49 branch.

    want a guess who's still using WinXP?.. yep, you probably guessed it ... pretty much any government-related institution around here is dumping Chrome like the proverbial hot potato and switching to Firefox.

    1. Anonymous Coward
      Anonymous Coward

      Re: NO, Google has NOT fixed the flaw for all Chrome users.

      Google has fixed the flaw for all supported Chrome users though.

      Except for expensive paid support contracts, Windows XP is not supported by even Microsoft now and hasn't been for over two years. POSReady 2009 is supported with security updates but is not licensed as a general purpose operating system, so there is absolutely no reason Google should continue to support XP.

      That said, unless obliged by a legally binding commitment, absolutely no third party vendor is required to support any operating system, regardless of original vendor support. Google also dropped support for Windows Vista, which is still supported by Microsoft until April 11, 2017. Mozilla are free to drop support any time they wish as well. The only browser guaranteed to receive security patches until the end of all Microsoft support contracts or the POSReady life cycle is in fact Internet Explorer. I would take little solace in that.

  5. Alan Denman

    NSA !

    the fact you cannot turn it off is a worry too.

    Anyone who supplies PDF or Docx by default ratger than plain readable text puts readers at risk!

    Downloads are always a risk!

  6. Mike Shepherd

    A tiny error

    "The flaw looks like it is down to a tiny error by Chrome's developers..."

    There are no "tiny errors" in today's computers. If you plan to get up on your hind legs and crow that you're taking over the world, you need to be careful with errors of any "size".

    If this flaw is so insignificant, why is it worthy of an article about it, particularly one which appears determined to play it down?

    I think it was Tony Hoare who wrote that "A programmer who uses assertions while testing and turns them off during production is like a sailor who wears a life vest while drilling on shore and takes it off at sea". Maybe Google could do with such basic notions of software quality.

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