CVE-2026-101338: high-severity vulnerability in NLnet Labs NSD
Stack overwrite from a specially crafted and formatted SVCB or HTTPS RR
Published
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 8.7epss 0.3%
When a SVCB or HTTPS RR has filled the wire format RDATA up to the brim, another ECH parameter may overwrite the stack, and once beyond the limit, the base64 decoder can write attacker controlled data of unlimited size. Zone files which are written out by NSD itself, such as for zones for which the NSD instance is secondary, will not be formatted like this. The zone file must be fed to NSD directly, (but it could come, for example, from an operator controlled provisioning system).
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Affected products
NLnet Labs · NSDRelated CVEs — NLnet Labs NSD
In the same product, most dangerous first.
CVE-2020-28935—Local symlink attack in Unbound and NSDEPSS 0.5%CVE-2026-12244HIGHHeap overflow and crash with crafted SVCB RREPSS 0.5%CVE-2026-19401HIGHRemote UDP DoS by sending multiple DNS Cookie optionsEPSS 0.5%CVE-2026-18916MEDIUMRemote TCP DoS by throttling the TCP receive windowEPSS 0.5%CVE-2026-12245HIGHDenial of DNS over TLS service by any DoT clientEPSS 0.5%CVE-2026-12246HIGHOut of bounds stack write with crafted APL RREPSS 0.4%