Red Hat Security Advisory: unbound security update
The unbound packages provide a validating, recursive, and caching DNS or DNSSEC resolver. Security Fix(es): * unbound: Unbound: Remote Code Execution Vulnerability in CNAME Synthesis (CVE-2026-82717) * unbound: Unbound: Heap buffer overflow via malicious DNSSEC response (CVE-2026-81634) * unbound: Unbound: Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY (CVE-2026-81642) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.
AI Analysis
Technical Summary
CVE-2026-81634 affects NLnet Labs Unbound up to and including version 1.26.0. The vulnerability is a heap buffer overflow caused by improper buffer length checking during the RRSet canonicalisation routine when processing a 255 length query name with a large TCP response. Specifically, the first owner name is omitted from the buffer length check, allowing an attacker who controls a malicious DNS server or can tamper with DNS responses to trigger the overflow before DNSSEC validation occurs.
Potential Impact
Successful exploitation can cause a heap buffer overflow leading to potential denial of service or other impacts on availability. The vulnerability does not impact confidentiality or integrity directly as per the CVSS vector, but it affects availability by causing crashes or instability in the Unbound DNS resolver.
Mitigation Recommendations
No patch or remediation information is provided in the input data. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid using untrusted DNS servers or intercepting DNS responses that could exploit this vulnerability.
Red Hat Security Advisory: unbound security update
Description
The unbound packages provide a validating, recursive, and caching DNS or DNSSEC resolver. Security Fix(es): * unbound: Unbound: Remote Code Execution Vulnerability in CNAME Synthesis (CVE-2026-82717) * unbound: Unbound: Heap buffer overflow via malicious DNSSEC response (CVE-2026-81634) * unbound: Unbound: Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY (CVE-2026-81642) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.
Affected software
pkg:deb/ubuntu/unbound?arch=source&distro=esm-infra-legacy/trustypkg:deb/ubuntu/unbound?arch=source&distro=esm-infra-legacy/xenialpkg:deb/ubuntu/unbound?arch=source&distro=esm-infra/bionicpkg:deb/ubuntu/unbound?arch=source&distro=esm-infra/focalpkg:deb/ubuntu/unbound?arch=source&distro=jammypkg:deb/ubuntu/unbound?arch=source&distro=noblepkg:deb/ubuntu/unbound?arch=source&distro=resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-81634 affects NLnet Labs Unbound up to and including version 1.26.0. The vulnerability is a heap buffer overflow caused by improper buffer length checking during the RRSet canonicalisation routine when processing a 255 length query name with a large TCP response. Specifically, the first owner name is omitted from the buffer length check, allowing an attacker who controls a malicious DNS server or can tamper with DNS responses to trigger the overflow before DNSSEC validation occurs.
Potential Impact
Successful exploitation can cause a heap buffer overflow leading to potential denial of service or other impacts on availability. The vulnerability does not impact confidentiality or integrity directly as per the CVSS vector, but it affects availability by causing crashes or instability in the Unbound DNS resolver.
Mitigation Recommendations
No patch or remediation information is provided in the input data. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid using untrusted DNS servers or intercepting DNS responses that could exploit this vulnerability.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-81634
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:Pro:14.04:LTS","Ubuntu:Pro:16.04:LTS","Ubuntu:Pro:18.04:LTS","Ubuntu:Pro:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:26.04:LTS"]
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ab4be4cf7a7c54106f06979
Added to database: 09/24/2026, 06:08:12 UTC
Last enriched: 09/24/2026, 06:43:41 UTC
Last updated: 09/25/2026, 05:02:00 UTC
Views: 5
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