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Date: Thu, 30 Jun 2016 15:25:16 +0800
From: Marcel Böhme <boehme.marcel@...il.com>
To: oss-security@...ts.openwall.com
Cc: florian@...h-krohm.de,
 nickc@...hat.com,
 Bernd Schmidt <bschmidt@...hat.com>
Subject: CVE Request: No demangling of untrusted binaries (2)

Hi all,

Another vulnerability in GNU Libiberty was found that impacts the security of binary analysis tools, such as Valgrind, GDB, Binutils (e.g., objdump, nm, ..), Gcov, or other LibBFD-based tools. An attacker might modify a program binary such that it executes malicious code upon *analysis* of the binary (e.g., to find whether it is malicious in the first place) or during the attempt to reverse-engineer an untrusted binary.

Workaround: Until the patches propagate to the vulnerable tools, switch off default demangling! E.g.,
$ echo "set demangle-style none"  >>  ~/.gdbinit
$ echo "--demangle=no" >> ~/.valgrindrc

A stackoverflow in the libiberty demangler causes its host application to crash on a tainted branch instruction. The problem is caused by a self-reference in a mangled type string that is "remembered" for later reference. This leads to an infinite recursion during the demangling.
* GDB exploitable classifies the stack overflow as exploitable.
* Bug Report: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71696
* Patch under review: https://gcc.gnu.org/ml/gcc-patches/2016-06/msg02030.html

All vulnerabilities were found with a more efficient version of the AFL fuzzer, called AFLFast.

Update on the previously reported, related vulnerabilities:
CVE-2016-2226: Fixed in trunk
CVE-2016-4487: Fixed in trunk
CVE-2016-4488: Fixed in trunk
CVE-2016-4489: Fixed in trunk
CVE-2016-4490: Fixed in trunk
CVE-2016-4491: Patch under review
CVE-2016-4492: Patch accepted
CVE-2016-4493: Patch accepted

Best regards,
- Marcel

---
Marcel Böhme
Post-doctoral Research Fellow
TSUNAMi Security Research Center
National University of Singapore

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