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CVE-2026-40622— Another 'ghost domain names' attack variant

Quick assessment

Affected
NLnet Labs Unbound
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.

NLnet Labs Unbound是NLnet Labs开源的一个高性能DNS解析器。 NLnet Labs Unbound 1.16.2版本至1.25.0版本存在访问控制错误漏洞，该漏洞源于幽灵域名攻击，可能导致攻击者通过控制幽灵区域并查询易受攻击的Unbound，将缓存过期父端引用NS记录集覆盖为子端顶点NS记录集，从而将幽灵域名窗口延长最多一个配置的缓存TTL值。

AI Predicted 5.9 Difficulty: Moderate EPSS 0.14% · P3

Possible ATT&CK Techniques 2 AI

T1071 · Application Layer Protocol T1435

Affected Version Matrix 1

VendorProduct Version RangeStatus
NLnet Labs Unbound 1.16.2< 1.25.1 affected
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I. Basic Information for CVE-2026-40622

Vulnerability Information
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Vulnerability Title
Another 'ghost domain names' attack variant
Source: CVE Program / CVE List V5
Vulnerability Description
NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
NLnet Labs Unbound 访问控制错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
NLnet Labs Unbound是NLnet Labs开源的一个高性能DNS解析器。 NLnet Labs Unbound 1.16.2版本至1.25.0版本存在访问控制错误漏洞，该漏洞源于幽灵域名攻击，可能导致攻击者通过控制幽灵区域并查询易受攻击的Unbound，将缓存过期父端引用NS记录集覆盖为子端顶点NS记录集，从而将幽灵域名窗口延长最多一个配置的缓存TTL值。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
NLnet Labs Unbound 1.16.2 ~ 1.25.1 -

II. Public POCs for CVE-2026-40622

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III. Intelligence Information for CVE-2026-40622

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Vendor Advisories for CVE-2026-40622 (1)

Same Patch Batch · NLnet Labs · 2026-05-20 · 11 CVEs total

CVE-2026-33278 9.1 CRITICAL Possible arbitrary code execution during DNSSEC validation
CVE-2026-42959 8.7 HIGH Crash during DNSSEC validation of malicious content
CVE-2026-42944 8.7 HIGH Heap overflow with multiple NSID, COOKIE, PADDING EDNS options
CVE-2026-42534 6.9 MEDIUM Jostle logic bypass degrades resolution performance
CVE-2026-44390 6.9 MEDIUM Unbounded name compression in certain cases causes degradation of service
CVE-2026-41292 6.6 MEDIUM Long list of incoming EDNS options degrades performance
CVE-2026-42923 Degradation of service with unbounded NSEC3 hash calculations
CVE-2026-42960 Possible cache poisoning via promiscuous records for the authority section
CVE-2026-32792 Packet of death with DNSCrypt
CVE-2026-44608 Use after free and crash under special conditions in RPZ code

IV. Related Vulnerabilities

Same product: Unbound
Same vendor: NLnet Labs

V. Comments for CVE-2026-40622

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