CVE-2026-101338

Stack overwrite from a specially crafted and formatted SVCB or HTTPS RR

Published Oct 14, 2026 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
Description
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).

Remediation

Vendor Solution

This issue is fixed in 4.15.3 and all later versions.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Nlnetlabs
Nlnetlabs nsd
Vendors & Products Nlnetlabs
Nlnetlabs nsd
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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).
Title Stack overwrite from a specially crafted and formatted SVCB or HTTPS RR
Weaknesses CWE-121
References
Metrics cvssV4_0

{'score': 8.7, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
NLnet Labs
Published
Updated
Oct 14, 2026, 2:09 PM
Reserved
Sep 28, 2026, 2:39 PM
Status
Awaiting Analysis
Published
Oct 14, 2026, 11:16 AM
Modified
Oct 16, 2026, 7:55 PM