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CVE-2026-101338— Stack overwrite from a specially crafted and formatted SVCB or HTTPS RR

Quick assessment

Affected
NLnet Labs NSD
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

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

CVSS 8.7 · High

Affected Version Matrix 1

VendorProduct Version RangeStatus
NLnet Labs NSD 4.10.0< 4.15.3 affected
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I. Basic Information for CVE-2026-101338

Vulnerability Information

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Vulnerability Title
Stack overwrite from a specially crafted and formatted SVCB or HTTPS RR
Source: CVE Program / CVE List V5
Vulnerability 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).
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
栈缓冲区溢出
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
NLnet Labs NSD 4.10.0 ~ 4.15.3 -

II. Public POCs for CVE-2026-101338

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III. Intelligence Information for CVE-2026-101338

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Other References for CVE-2026-101338 (1)

Same Patch Batch · NLnet Labs · 2026-10-14 · 4 CVEs total

CVE-2026-101337 8.7 HIGH Stack overwrite from specially formatted base64 RDATA field
CVE-2026-101341 8.7 HIGH Stack overwrite from specially formatted TXT-DATA RDATA field
CVE-2026-101339 8.7 HIGH Stack overwrite from a specially crafted and formatted HIP RR

IV. Related Vulnerabilities

Same product: NSD
Same vendor: NLnet Labs
Same weakness: CWE-121

V. Comments for CVE-2026-101338

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