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Date: Thu, 28 Sep 2023 17:49:08 +0200
From: Emilio Pozuelo Monfort <>
Subject: Re: CVE-2023-4863: libwebp: Heap buffer overflow in
 WebP Codec

On 28/09/2023 14:36, Jeffrey Walton wrote:
> On Tue, Sep 26, 2023 at 11:37 AM Solar Designer <> wrote:
>> It was great to hear from Vincent that the newer libwebp changes are
>> just "Clean-ups, no security issues there."  Yet I think it would also
>> be great if someone in here double-checks that.
>> Regarding the assert failure detected by oss-fuzz, "A release build
>> would not be negatively affected."  libwebp does specify -DNDEBUG by
>> default in:
>> $ fgrep -rl DNDEBUG .
>> ./
>> ./
>> ./
>> ./
>> ./makefile.unix
>> and there's also cmake support, but apparently cmake sets -DNDEBUG for
>> release builds by default.  So at least this statement does appear to be
>> true for libwebp itself as built via the above means.
>> However, there's also Gradle support, and the gradle* files do not
>> mention NDEBUG.
>> Also, I wonder if there are other projects building code from libwebp
>> via different build environments.
>> So there might be (a small minority of) uses of libwebp where the assert
>> exists in a release build of some project.
> Crypto++ caught a CVE because use of -DNDEBUG was not documented. The
> library's build system used -DNDEBUG (like libwebp), but folks who
> ported to other build systems did not use it. In my mind's eye, others
> who did not use the -DNDEBUG flag should have caught a CVE, not
> Crypto++. Also see CVE-2016-7420 and
> <>.
> Crypto++ eventually took away the footgun by supplying its own
> CRYPTOPP_ASSERT that required a user to supply a switch to engage
> asserts. Asserts were no longer enabled by default when someone
> omitted -DNDEBUG. Also see
> <>.
> I've never seen a CVE for documentation before or since.

Here's a recent one:;a=commitdiff;h=51e8a84ce742db0f6c70510d0159dad8f7825908


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