{"id":82398,"date":"2026-07-22T16:40:24","date_gmt":"2026-07-22T13:10:24","guid":{"rendered":"https:\/\/afaghhosting.net\/blog\/cve-2026-56416-possible-heap-buffer-overflow-when-validator-canonicalizes-rdata-that-contains-domain-name\/"},"modified":"2026-07-22T16:40:24","modified_gmt":"2026-07-22T13:10:24","slug":"cve-2026-56416-possible-heap-buffer-overflow-when-validator-canonicalizes-rdata-that-contains-domain-name","status":"publish","type":"post","link":"https:\/\/afaghhosting.net\/blog\/cve-2026-56416-possible-heap-buffer-overflow-when-validator-canonicalizes-rdata-that-contains-domain-name\/","title":{"rendered":"CVE-2026-56416 &#8211; Possible heap buffer overflow when validator canonicalizes RDATA that contains domain name"},"content":{"rendered":"<p>CVE ID :CVE-2026-56416<\/p>\n<p>  Published : July 22, 2026, 1:10 p.m. | 35\u00a0minutes ago<\/p>\n<p>  Description :In NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX\/RP\/MINFO\/SOA RRset, it computes the address of the second embedded domain name as &#8216;datstart + dname_valid(datstart, &#8230;)&#8217; and passes it straight to &#8216;query_dname_tolower()&#8217; without checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server can deliver a record with an absent second domain name (e.g. SOA record) and cause &#8216;query_dname_tolower()&#8217; to walk label-by-label through stale bytes in the per-worker &#8216;env-&gt;scratch_buffer&#8217;, past the end of that heap allocation if &#8216;msg-buffer-size&#8217; has been lowered from the default. This leads to heap buffer overflow and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap chunk.<\/p>\n<p>  Severity: 4.8 | MEDIUM<\/p>\n<p>  Visit the link for more details, such as CVSS details, affected products, timeline, and more&#8230;\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"<p>CVE ID :CVE-2026-56416 Published : July 22, 2026, 1:10 p.m. | 35\u00a0minutes ago Description :In NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX\/RP\/MINFO\/SOA RRset, it computes the address of the second embedded domain name as &#8216;datstart + dname_valid(datstart, &#8230;)&#8217; and passes it &hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[],"class_list":["post-82398","post","type-post","status-publish","format-standard","hentry","category-vulnerability"],"_links":{"self":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts\/82398","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/comments?post=82398"}],"version-history":[{"count":0,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts\/82398\/revisions"}],"wp:attachment":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/media?parent=82398"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/categories?post=82398"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/tags?post=82398"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}