Packet of death for DNSCrypt over TCP (NLnet Labs Unbound)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.29 % · percentile 22 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- NLnet Labs
- NVD status
- Analyzed
Description
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 ('--enable-dnscrypt') and the 'dnscrypt:' clause to be configured and enabled for the listening interfaces.
Weaknesses (CWE)
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | NLnet Labs |
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | NVD · sep@nlnetlabs.nl (Secondary) |
European references
- ENISA EUVD · EUVD-2026-47664
- GCVE · GCVE-0-2026-40691
Affected configurations (NVD CPE)
cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*≥ 1.9.0 < 1.25.2
Affected products
| Product | Versions |
|---|---|
| NLnet Labs · Unbound | affected 1.9.0 < 1.25.2 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |