Bug 1535038

Summary: glibc: Stack canary bypass via pthread_create()
Product: [Other] Security Response Reporter: Pedro Sampaio <psampaio>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED WONTFIX QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: aoliva, arjun.is, ashankar, codonell, dj, fweimer, glibc-bugzilla, law, mfabian, mnewsome, pfrankli, rth, security-response-team, siddhesh, tcallawa
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: If docs needed, set a value
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Clone Of: Environment:
Last Closed: 2018-02-26 00:32:37 UTC Type: ---
Regression: --- Mount Type: ---
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Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1535039, 1535040, 1546606, 1546607    
Bug Blocks: 1535678    

Description Pedro Sampaio 2018-01-16 14:24:22 UTC 
A flaw in glibc stack protection feature was found. The canary value is located in structure 'tcbhead_t' field 'stack_guard'. If a application create a new thread with pthread_create() function, tcbhead_t structure will be placed on the top of the stack thread, making it vulnerable to corruption a bypass of stack protection.
Comment 12 Doran Moppert 2018-02-19 01:43:51 UTC 
Upstream bug:

https://sourceware.org/bugzilla/show_bug.cgi?id=22850

Previous discussions:

http://bases-hacking.org/tcb-overwrite.html
http://blog.talosintelligence.com/2016/01/bypassing-miniupnp-stack-smashing.html
Comment 13 Doran Moppert 2018-02-19 01:48:27 UTC 
Created glibc tracking bugs for this issue:

Affects: fedora-all [bug 1546607]


Created glibc-arm-linux-gnu tracking bugs for this issue:

Affects: fedora-all [bug 1546606]
Comment 14 Doran Moppert 2018-02-19 02:14:17 UTC 
Statement:

This flaw is a weakness in -fstack-protector, which is a post-exploitation mitigation of stack buffer overflows. Under specific circumstances, this flaw can allow an attacker to bypass the stack canary. Most often, exploits of this kind are effectively mitigated by FORTIFY_SOURCE, which will detect the attempted overflow before the stack-protector check occurs. The protections offered by FORTITY_SOURCE are not impacted by this flaw.