{"id":"AZL-92940","summary":"CVE-2026-56416 affecting package unbound for versions less than 1.25.2-1","details":"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 'datstart + dname_valid(datstart, ...)' and passes it straight to 'query_dname_tolower()' 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 'query_dname_tolower()' to walk label-by-label through stale bytes in the per-worker 'env-\u003escratch_buffer', past the end of that heap allocation if 'msg-buffer-size' 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.","modified":"2026-08-28T17:47:53.542892547Z","published":"2026-07-22T14:17:22Z","upstream":["CVE-2026-56416"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-56416"}],"affected":[{"package":{"name":"unbound","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/unbound"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.25.2-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-92940.json"}}],"schema_version":"1.9.0"}