Bug 1952674 (CVE-2021-29136)

Summary: CVE-2021-29136 singularity: allows overwriting of host files
Product: [Other] Security Response Reporter: Guilherme de Almeida Suckevicz <gsuckevi>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED UPSTREAM QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: bbockelm, dave.love, dwd
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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Last Closed: 2021-04-22 22:46:33 UTC Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 1946970, 1952675, 1952676    
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Description Guilherme de Almeida Suckevicz 2021-04-22 20:19:55 UTC 
This vulnerability is in umoci but it was found that singularity is also affected.

A dependency used by Singularity to extract docker/OCI image layers can be tricked into modifying host files by creating a malicious layer that has a symlink with the name "." (or "/"), when running as root. This vulnerability affects a singularity build or singularity pull as root, from a docker or OCI source, as well as the implicit build to SIF that occurs through root use of run/exec/shell against a malicious docker/OCI image URI.

Reference:
https://github.com/hpcng/singularity/releases
Comment 1 Guilherme de Almeida Suckevicz 2021-04-22 20:20:21 UTC 
Created singularity tracking bugs for this issue:

Affects: epel-all [bug 1952676]
Affects: fedora-all [bug 1952675]
Comment 2 Dave Dykstra 2021-04-22 21:56:06 UTC 
This is being addressed in #1946970
Comment 3 Product Security DevOps Team 2021-04-22 22:46:33 UTC 
This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.