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CVE-2026-81642— Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY

Quick assessment

Affected
NLnet Labs Unbound
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in the DNSSEC validator that enables denial of service and possible remote code execution as a result of digesting DNSKEYs. A DNSKEY with an owner compression pointer to its own RDATA

CVSS 9.1 · Critical
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I. Basic Information for CVE-2026-81642

Vulnerability Information
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Vulnerability Title
Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY
Source: CVE Program / CVE List V5
Vulnerability Description
In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in the DNSSEC validator that enables denial of service and possible remote code execution as a result of digesting DNSKEYs. A DNSKEY with an owner compression pointer to its own RDATA can overflow the digest buffer. Remote code execution is possible through attacker controlled data. An adversary can exploit the vulnerability by controlling a malicious zone and querying a vulnerable Unbound.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/U:Red
Source: CVE Program / CVE List V5
Vulnerability Type
堆缓冲区溢出
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
NLnet Labs Unbound 0 ~ 1.26.1 -

II. Public POCs for CVE-2026-81642

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III. Intelligence Information for CVE-2026-81642

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Other References for CVE-2026-81642 (1)

Same Patch Batch · NLnet Labs · 2026-09-16 · 9 CVEs total

CVE-2026-82717 8.4 HIGH CNAME synthesis could lead to heap corruption
CVE-2026-81634 7.5 HIGH Possible heap buffer overflow during DNSSEC canonicalization
CVE-2026-78227 6.5 MEDIUM Use-after-free in DoQ stream output buffer on reset re-transmission
CVE-2026-82720 5.9 MEDIUM Use-after-free in DoH stream cleanup code path
CVE-2026-85501 5.3 MEDIUM Retrap: Novel Vulnerabilities to launch Algorithmic Complexity Attacks on DNSSEC
CVE-2026-80225 5.3 MEDIUM Possible degradation of service from continuous queries on the same TCP/DoT connection
CVE-2026-77955 4.4 MEDIUM Possible ZONEMD verification bypass window
CVE-2026-77860 3.7 LOW 'serve-expired' can bypass Unbound 'wait-limit'

IV. Related Vulnerabilities

Same product: Unbound
Same vendor: NLnet Labs
Same weakness: CWE-122

V. Comments for CVE-2026-81642

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