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CVE-2026-81634 is a heap buffer overflow in NLnet Labs Unbound's RRSet canonicalisation routine affecting releases through 1.26.0. When processing a maximum-length (255-byte) query name together with a large TCP DNS response, the buffer-length calculation fails to account for the first owner name. Canonicalisation occurs before DNSSEC validation, allowing a malicious upstream name server or an on-path actor able to alter an inbound DNS response to reach the vulnerable code path.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
8 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A high-severity Unbound denial-of-service flaw triggered by a 255-byte query name combined with a large TCP response supplied by a malicious name server or a tampered response.
A possible heap buffer overflow in DNSSEC canonicalization.
A possible heap buffer overflow in Unbound's DNSSEC canonicalization handling.
A possible heap buffer overflow in Unbound's DNSSEC canonicalization handling.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.