Date: Fri, 28 Nov 2014 10:20:39 +0000 From: John Haxby <john.haxby@...cle.com> To: oss-security@...ts.openwall.com CC: xi@...olvent.net, ingy@...n.org Subject: Re: libyaml / YAML-LibYAML DoS On 28/11/14 05:57, Jonathan Gray wrote: > libyaml and the perl YAML-LibYAML (aka YAML-XS) module based > on the same code have an "impossible" assert that can be > triggered with the following yaml. This is a reduced testcase > of a crash found with the afl fuzzer. > > a: " > " b: true > > In other words a crash/denial of service with untrusted yaml input. > The libyaml author was contacted on the 21st and 27th of November. > No response has been received but the issue has independently been > reported publically since: > https://bitbucket.org/xi/libyaml/issue/10/wrapped-strings-cause-assert-failure > >  Parsing 'test.yaml': assertion "parser->simple_key_allowed || !required" failed: file "scanner.c", line 1113, function "yaml_parser_save_simple_key" > > assert(parser->simple_key_allowed || !required); /* Impossible. */ For what it's worth PyYAML 3.10 and 3.11 have exactly the same assertion: >>> import yaml >>> yaml.load(""" ... abc: ... def: 'xxx ... ' ghi: 'yyy' ... """) Traceback (most recent call last): [...] assert self.allow_simple_key or not required AssertionError jch
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