In Unbound 1.9.0 up to and including 1.25.1, when a DNSCrypt query is received over TCP, the routine that encrypts the reply in place fails to bound…
In Unbound 1.9.0 up to and including 1.25.1, when a DNSCrypt query is received over TCP, the routine that encrypts the reply in place fails to bound the reply length against the destination buffer size. The size clamp that protects the UDP path is not applied on the TCP path, so a reply larger than 65504 bytes is shifted forward by 48 bytes inside a buffer of capacity equal to 'msg-buffer-size', writing past the end of the heap allocation. A single malicious encrypted query crashes the resolver and lead to denial of service. This vulnerability needs Unbound to be compiled with DNSCrypt support
Read at NIST National Vulnerability Database (CVE API 2.0)
- Product
- dnsmasq / Unbound / PowerDNS
- CVSS
- 7.5
- EPSS
- 0.003 (p22)
- Exposure class
- Edge / VPN / firewall
Why it ranks 34 (Notable)
- CVSS 7.5 high
- Exposed product class: edge / VPN / firewall
- Covered by 3 independent sources
- Recency: items published within 24 hours gain 15, within 72 hours 6, within 7 days 2.
Links
- NIST National Vulnerability Database (CVE API 2.0) (nvd.nist.gov)
- CVE-2026-40691 on this site · NVD · CVE.org · Vulnpedia
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