Bug 2535051 (CVE-2026-82717)

Summary: CVE-2026-82717 unbound: Unbound: Remote Code Execution Vulnerability in CNAME Synthesis
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in Unbound. Improper handling of buffer positions and compression pointers in Unbound's CNAME synthesis allows a remote attacker to corrupt heap memory via upstream DNS responses. This vulnerability can result in a denial of service (DoS) or, under specific conditions, remote code execution (RCE).
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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: 2536903    
Bug Blocks:    

Description OSIDB Bzimport 2026-09-16 09:00:43 UTC 
In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in that can progressively corrupt heap memory and under certain systems and compilation options could lead to remote code execution. The vulnerability starts when CNAME synthesis during an upstream response needs to enforce(rewrite) a max TTL value in the packet buffer. Coupled with a compression pointer that points to the overwritten value and invalidates the domain name, it leads to an error path that does not properly move the buffer position and allows for the heap buffer overflow. Since this is heavily reliant on heap memory layout, results are memory corruption that eventually leads to a crash and under specific systems and compilation options remote code execution.
Comment 3 Jon Orris 2026-09-23 13:22:24 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:70754 https://access.redhat.com/errata/RHSA-2026:70754
Comment 4 Jon Orris 2026-09-24 09:06:52 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:71419 https://access.redhat.com/errata/RHSA-2026:71419
Comment 5 Jon Orris 2026-09-24 16:39:14 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:71487 https://access.redhat.com/errata/RHSA-2026:71487
Comment 7 Jon Orris 2026-10-06 12:01:11 UTC 
This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.22

Via RHSA-2026:74428 https://access.redhat.com/errata/RHSA-2026:74428