Sunday, 11 November 2018

null-pointer dereference in poppler library - CVE-2018-19149

Hi Internet,

Summary: While fuzzing evince v3.28.4, on linux 4.15.0-38-generic (Ubuntu 18.04 LTS), a null-pointer dereference was observed, initially this was reported to evince but the evince team advised that the issue is in poppler, the library used by evince to render PDF, poppler version: 0.62.0-2ubuntu2.2 is vulnerable to null-pointer dereference, however the issue is already fixed in poppler 0.70, but this will still crash your evince v3.28.4 if poppler is not updated to v.0.70. Fuzzing result showing a very important vulnerability in a package currently shipped by a major Linux distribution is still of interest, even if that Linux distribution does not package the latest released upstream version.

Initially, I started fuzzing with evince which is a document reader which comes by default with most of the linux distribution. Also created a malformed PDF files to provide input to AFL, after a successfully compile of evince with afl-gcc, the final command was,

It took three days to get 21 crashes in which 6 unique crashes where observed, while analyzing the crash with triage_crashes which is one of the component which comes with AFL for analyzing crashes, I observed a null-PTR.

So basically a null-PTR is a type of error which causes a SIGSEGV, segmentation fault to the program, and this usually happens when a program or binary try to read or write to the memory with null-PTR.

I went ahead and reported this to GNOME, because evince is one of there asset, the team says "The issue is in Poppler, the library used by Evince to render PDF" arggh!, so stupid am I, I taught `` is one of the shared object in evince but didn't know that poppler is a PDF rendering library which comes by default in most of the PDF reader in linux distribution, and there is a standalone repo out there for poppler.

Also, GNOME evince team says "it seems it has already been addressed. See, Nevertheless, if the issue is still present, please file a bug in"

Okay no worries, I still went ahead and file a bug in poppler, but the team over there asked me what poppler version am i using, and it was version 0.62.0-2ubuntu2.2 and they said the issue is already fixed in poppler version 0.70 After I read this, I was like....
Img Src:

Pheww!, does that mean, my three days of fuzzing just went = to 0 OR am I actually missing something over here ?

I went back to the stack-trace read it again and also check whether am I fuzzing all the latest build of the binary for sure I was fuzzing the latest build of evince but not poppler. Hmmmmmm! I knew my fuzzing system was fully updated but still just to cross check, I did full apt-get update and upgrade but my poppler version remains the same all the time which is 0.62.0-2ubuntu2.2 strange.

I need a guidance over here, and didn't knew what to do ahead, so I contacted MITRE for this and went for a nap, they suggested - "That a fuzzing result showing a very important vulnerability in a package currently shipped by a major Linux distribution is still of interest, even if that Linux distribution does not package the latest released upstream version. For example, an out-of-bounds write finding is still very useful in that case, but not out-of-bounds read, NULL pointer dereference,divide-by-zero, etc."

Ohhh, I see so the latest version of poppler is still not shipped for most of the linux distribution out there, now i understood the entire concept, later MITRE also helped me by assigning a CVE to this issue which is CVE-2018-19149 - Poppler before 0.70.0 has a NULL pointer dereference in _poppler_attachment_new when called from poppler_annot_file_attachment_get_attachment.

PS: Its not about collecting CVE's, CVE's are just a reference number to an issue you can point for a vulnerability when you show case it somewhere, rather than pointing it to various post. (Personal opinion).

Lessons learned from this:
1. I didn't know poppler is a library which is used by evince and other PDF reader to render PDF's.
2. I understood how to create a malformed PDF to provide input to AFL while fuzzing.
3. The reply from MITRE helped me to resolve my query.
4. During all this, I also got my hands on hongfuzz

Hope you like the read, view this on oss-security mailing list.

Thank you

Tuesday, 6 November 2018

Fuzzing IEC 61850 protocol - CVE-2018-18957

Hi Internet,

Summary: While fuzzing(I've used AFL for this), a stack based buffer overflow was found in libIEC61850 (the open-source library for the IEC 61850 protocols) in prepareGooseBuffer in goose/goose_publisher.c and /linux/ethernet_linux.c

Steps to reproduce:
$ ./goose_publisher_example crash_goosecr_stack_smash_overflow_aaaaaaaaa
Using interface crash_goosecr_stack_smash_overflow_aaaaaaaaa
*** stack smashing detected ***:  terminated
File: crash_goosecr_stack_smash_overflow_aaaaaaaaa
[This file will be expired after 30 days.]

(gdb) run crash_goosecr_stack_smash_overflow_aaaaaaaaa
Starting program:
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/".
Using interface crash_goosecr_stack_smash_overflow_aaaaaaaaa
*** stack smashing detected ***:  terminated

Program received signal SIGABRT, Aborted.
__GI_raise (sig=sig@...ry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
51    ../sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0  __GI_raise (sig=sig@...ry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1  0x00007ffff7805801 in __GI_abort () at abort.c:79
#2  0x00007ffff784e897 in __libc_message (action=action@...ry=do_abort,
fmt=fmt@...ry=0x7ffff797b988 "*** %s ***: %s terminated\n")
    at ../sysdeps/posix/libc_fatal.c:181
#3  0x00007ffff78f9cd1 in __GI___fortify_fail_abort
    msg=msg@...ry=0x7ffff797b966 "stack smashing detected") at
#4  0x00007ffff78f9c92 in __stack_chk_fail () at stack_chk_fail.c:29
#5  0x000055555555a211 in Ethernet_getInterfaceMACAddress
(interfaceId=0x7fffffffdeee "crash_goosecr_stack_smash_overflow_aaaaaaaaa",
    addr=0x7fffffffd91c "k_smas\377\377") at
#6  0x00005555555594ee in prepareGooseBuffer (self=0x5555557637d0,
"crash_goosecr_stack_smash_overflow_aaaaaaaaa") at
#7  0x0000555555559293 in GoosePublisher_create (parameters=0x7fffffffd9ac,
"crash_goosecr_stack_smash_overflow_aaaaaaaaa") at
#8  0x0000555555555387 in main (argc=2, argv=0x7fffffffdaa8) at
(gdb) i r
rax            0x0    0
rbx            0x7fffffffd6b0    140737488344752
rcx            0x7ffff7803e97    140737345765015
rdx            0x0    0
rsi            0x7fffffffd410    140737488344080
rdi            0x2    2
rbp            0x7fffffffd840    0x7fffffffd840
rsp            0x7fffffffd410    0x7fffffffd410
r8             0x0    0
r9             0x7fffffffd410    140737488344080
r10            0x8    8
r11            0x246    582
r12            0x7fffffffd6b0    140737488344752
r13            0x1000    4096
r14            0x0    0
r15            0x30    48
rip            0x7ffff7803e97    0x7ffff7803e97 <__gi_raise>
eflags         0x246    [ PF ZF IF ]
cs             0x33    51
ss             0x2b    43
ds             0x0    0
es             0x0    0
fs             0x0    0
gs             0x0    0
Snip : src/goose/goose_publisher.c
    GoosePublisher self = (GoosePublisher) GLOBAL_CALLOC(1, sizeof(struct sGoosePublisher));
    prepareGooseBuffer(self, parameters, interfaceID);
    self->timestamp = MmsValue_newUtcTimeByMsTime(Hal_getTimeInMs());
    return self;
Snip: src/goose/goose_publisher.c
    if (interfaceID != NULL)
        Ethernet_getInterfaceMACAddress(interfaceID, srcAddr);
Ethernet_getInterfaceMACAddress(CONFIG_ETHERNET_INTERFACE_ID, srcAddr);
Snip: /linux/ethernet_linux.c
strcpy(buffer.ifr_name, interfaceId);
Later CVE-2018-18957 was assigned to this issue, Read this on oss-security.

Thank you

Thursday, 18 October 2018

Porting CVE-2018-8120 to an MSF module

Hi Internet,

I have added the support of CVE-2018-8120 to MSF module, before porting this to MSF I read through the analysis of the issue.

After reading the blog post of xiaodaozhi I understood CVE-2018-8120 happens because of a null pointer dereference in the win32k kernel module at start this would lead to BSOD in vulnerable systems, however the exploit code was written in such a fashion that would override the function pointer which is present in kernel mode that achieves escalation of privilege to the remote or your local system.

It took me a while to port this to an MSF module also I would like to thank MSF team for there review's done during that time, at last this was successfully ported and landed!

The path for this module will be `exploit/windows/local/ms18_8120_win32k_privsec.rb` view this in action. (Sweeeeeeet!)
This module was tested against windows 7 x64 and x86 based systems and windows server 2008 R2 x64. However this vulnerability impacts following software versions or editions which are affected.

Thank you

Saturday, 29 September 2018

Telegram anonymity fails in desktop - CVE-2018-17780

Hi Internet,

Summary: Strangely tdesktop 1.3.14 and Telegram for windows ( WP8.1) leaks end user private and public IP address while making calls. This bug was awarded €2000 by Telegram security team. (Sweeet..)
Img Src:
Telegram is supposedly a secure messaging application, but it forces clients to only use P2P connection while initiating a call, however this setting can also be changed from "Settings > Privacy and security > Calls > peer-to-peer" to other available options. The tdesktop and telegram for windows breaks this trust by leaking public/private IP address of end user and there was no such option available yet for setting "P2P > nobody" in tdesktop and telegram for windows.

PS: Even telegram for android will also leak your IP address if you have not set "Settings > Privacy and security > Calls > peer-to-peer > nobody" (But Peer-to-Peer settings for call option already exists in telegram for android).

To view this in action in tdesktop:
1. Open tdesktop,
2. Initiate a call to anyone,
3. You will notice the end user IP address is leaking.

Other scenario:
1. Open tdesktop in Ubuntu and login with user A
2. Open telegram in windows phone login with user B
3. Let user B initiate the call to user A
4. While user A access log will have public/private IP address of user B.
Not only the MTProto Mobile Protocol fails here in covering the IP address, rather such information can also be used for OSINT. This issue was fixed in 1.3.17 beta and v1.4.0 which have an option of setting your "P2P to Nobody/My contacts", Later CVE-2018-17780 was assign to this vulnerability.


Thursday, 27 September 2018

Telegram uses SOCKS5 to share user/creds

Hi Internet,

Summary: Telegram is supposedly is a secure messaging application but it uses SOCKS5 to transmit user credential's, neither traffic nor credentials are encrypted in the SOCKS5 protocol, but this is how the SOCKS protocol works (see, SOCKS5 carries passwords in cleartext. Telegram team is aware with this and says its working has intended.
Img Src:

Product affected: tdesktop 1.3.16 alpha, Browser Info: Firefox 62.0 (64 bit), Tested on: Ubuntu 18.04 LTS x64

Steps to reproduce the issue:
1. Open tdesktop
2. Go to Settings > Advanced Settings > Connection type
3. Open "Proxy Settings" check "Use proxy"
4. Put some random Hostname, Port, Username and Password
5. tdesktop tries to connect it, while it connects click on that line which is made of 3 small spots (On right hand side)
6. Click share, the link gets copied.

Example Link: 

The link which gets generated have the password in plaintext, SOCKS5 is a transport protocol and by itself it is not encrypted. Requests transmitting such  credentials in plain text are considered as a bad security practice.

However, the URL which gets generated via telegram is in HTTPS but, URI producers should not provide a URI that contains a username or password that is intended to be secret.  URIs are frequently displayed by browsers, stored in clear text bookmarks, and logged by user agent history and intermediary applications (proxies).

Read this on oss sec-lists. Later CVE-2018-17613 was assigned to this issue.