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Date: Sat, 5 Nov 2016 10:04:30 -0300
From: Gustavo Grieco <gustavo.grieco@...il.com>
To: oss-security@...ts.openwall.com
Subject: CVE request: Null pointer derefence parsing xml file using libxml
 2.9.4 (in recover mode)

Hi,

We found a null pointer dereference when parsing a xml file using recover
mode. It was tested in libxml 2.9.4 (ArchLinux x86_64). To reproduce:

$ xmllint --recover crash-libxml2-recover.xml

==27646==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000
(pc 0x0000004fbd88 bp 0x7ffc3345dff0 sp 0x7ffc3345dfd0 T0)
    #0 0x4fbd87 in xmlDumpElementContent
/home/g/Work/Code/libxml2-2.9.4/valid.c:1181
    #1 0x4fbcd5 in xmlDumpElementContent
/home/g/Work/Code/libxml2-2.9.4/valid.c:1177
    #2 0x4fe5ff in xmlDumpElementDecl
/home/g/Work/Code/libxml2-2.9.4/valid.c:1706
    #3 0x72e714 in xmlBufDumpElementDecl
/home/g/Work/Code/libxml2-2.9.4/xmlsave.c:501
    #4 0x73048f in xmlNodeDumpOutputInternal
/home/g/Work/Code/libxml2-2.9.4/xmlsave.c:939
    #5 0x72fc47 in xmlNodeListDumpOutput
/home/g/Work/Code/libxml2-2.9.4/xmlsave.c:825
    #6 0x72f6d5 in xmlDtdDumpOutput
/home/g/Work/Code/libxml2-2.9.4/xmlsave.c:749
    #7 0x73038f in xmlNodeDumpOutputInternal
/home/g/Work/Code/libxml2-2.9.4/xmlsave.c:931
    #8 0x732412 in xmlDocContentDumpOutput
/home/g/Work/Code/libxml2-2.9.4/xmlsave.c:1234
    #9 0x735883 in xmlSaveDoc /home/g/Work/Code/libxml2-2.9.4/xmlsave.c:1936
    #10 0x40ba0f in parseAndPrintFile
/home/g/Work/Code/libxml2-2.9.4/xmllint.c:2712
    #11 0x411eb6 in main /home/g/Work/Code/libxml2-2.9.4/xmllint.c:3767
    #12 0x7f23dcd4c290 in __libc_start_main (/usr/lib/libc.so.6+0x20290)
    #13 0x4032b9 in _start
(/home/g/Work/Code/libxml2-2.9.4/xmllint+0x4032b9)


A reproducer is attached. It is interesting to note that the developers of
libxml2 strongly recommend not to use recover mode to parse untrusted
inputs. Please assign a CVE if suitable.

Regards,
Gustavo.

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View attachment "crash-libxml2-recover.xml" of type "text/xml" (803 bytes)

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