SB2026092378 - Red Hat Enterprise Linux 8 update for unbound
Published: September 23, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 3 vulnerabilities.
1) Heap-based buffer overflow (CVE-ID: CVE-2026-82717)
CWE-ID: CWE-122 - Heap-based Buffer Overflow
CVSSv4: 9.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to a heap-based buffer overflow in the CNAME synthesis packet-buffer handling logic when processing a crafted upstream DNS response that requires max TTL rewriting. A remote attacker can send a specially crafted upstream DNS response to execute arbitrary code.
Successful code execution depends on the system configuration, compilation options, and heap memory layout.
2) Heap-based buffer overflow (CVE-ID: CVE-2026-81634)
CWE-ID: CWE-122 - Heap-based Buffer Overflow
CVSSv4: 0 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to cause memory corruption.
The vulnerability exists due to improper buffer length validation in the RRSet canonicalisation routine when processing a 255-length query name with a large TCP response. A remote attacker can provide a crafted DNS response to cause memory corruption.
Canonicalisation occurs before DNSSEC validation.
3) Out-of-bounds write (CVE-ID: CVE-2026-81642)
CWE-ID: CWE-787 - Out-of-bounds write
CVSSv4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to execute arbitrary code or cause a denial of service.
The vulnerability exists due to a buffer overflow in Unbound's DNSSEC validator when processing a DNSKEY with an owner compression pointer to its own RDATA. A remote attacker can control a malicious zone and query a vulnerable Unbound instance to execute arbitrary code or cause a denial of service.
Remediation
Install update from vendor's website.