Bug 1979664 (CVE-2021-36085)

Summary: CVE-2021-36085 libsepol: use-after-free in __cil_verify_classperms()
Product: [Other] Security Response Reporter: Guilherme de Almeida Suckevicz <gsuckevi>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: caswilli, dwalsh, fjansen, jnakfour, kaycoth, lvrabec, mmalik, plautrba, psegedy, vmojzis, vmugicag
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Last Closed: 2021-11-10 00:23:22 UTC Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On: 1979665, 1983519, 1983520, 1983521, 1983522, 1984148    
Bug Blocks: 1979670    

Description Guilherme de Almeida Suckevicz 2021-07-06 16:51:58 UTC
The CIL compiler in SELinux 3.2 has a use-after-free in __cil_verify_classperms (called from __verify_map_perm_classperms and hashtab_map).

References:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=31124
https://github.com/google/oss-fuzz-vulns/blob/main/vulns/selinux/OSV-2021-421.yaml

Upstream patch:
https://github.com/SELinuxProject/selinux/commit/2d35fcc7e9e976a2346b1de20e54f8663e8a6cba

Comment 1 Guilherme de Almeida Suckevicz 2021-07-06 16:52:23 UTC
Created libsepol tracking bugs for this issue:

Affects: fedora-all [bug 1979665]

Comment 4 Garrett Tucker 2021-07-26 15:18:21 UTC
selinux/libsepol is mostly local access and to perform this attack would require local access as compared to network access. An attacker would also require some form of privileges to write the policy file and compile the CIL. The availability impact is also low as this flaw would not cause a system wide or complete lack of availability. Instead the attack would only impact availability of selinux temporarily.

Comment 5 errata-xmlrpc 2021-11-09 19:03:29 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:4513 https://access.redhat.com/errata/RHSA-2021:4513

Comment 6 Product Security DevOps Team 2021-11-10 00:23:20 UTC
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2021-36085