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CVE-2026-54478— DNS Cookie bypass when combined with proxy-protocol use

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是荷兰NLnet Labs组织的域名系统解析服务器。 NLnet Labs Unbound 1.18.0版本至1.25.1版本存在授权问题漏洞，该漏洞源于当Unbound在'proxy-protocol-port'接口上监听并启用'answer-cookie: yes'时，RFC 9018服务器cookie的SipHash基于代理的线路地址而非PROXYv2声明的客户端进行计算，导致通过给定代理节点获取的一个服务器cookie可验证该节点后的每个PROXYv2声明源，路

CVSS 3.7 · Low EPSS 0.24% · P14

Possible ATT&CK Techniques 1 AI

T1498 · Network Denial of Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
NLnet Labs Unbound 1.18.0< 1.25.2 affected
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I. Basic Information for CVE-2026-54478

Vulnerability Information
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Vulnerability Title
DNS Cookie bypass when combined with proxy-protocol use
Source: CVE Program / CVE List V5
Vulnerability Description
In NLnet Labs Unbound 1.18.0 up to and including 1.25.1, when Unbound listens on a 'proxy-protocol-port' interface with 'answer-cookie: yes', the RFC 9018 server-cookie SipHash is computed over the proxy's wire address instead of the PROXYv2-declared client. One server cookie obtained through a given proxy node therefore validates for every PROXYv2-declared source behind that node. On a UDP+proxy-protocol front, an off-path attacker can harvest one cookie with a single legitimate query, then replay it under any spoofed source and pass DNS Cookie checks that were deployed to defeat this in the first place.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
使用欺骗进行的认证绕过
Source: CVE Program / CVE List V5
Vulnerability Title
NLnet Labs Unbound 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
NLnet Labs Unbound是荷兰NLnet Labs组织的域名系统解析服务器。 NLnet Labs Unbound 1.18.0版本至1.25.1版本存在授权问题漏洞，该漏洞源于当Unbound在'proxy-protocol-port'接口上监听并启用'answer-cookie: yes'时，RFC 9018服务器cookie的SipHash基于代理的线路地址而非PROXYv2声明的客户端进行计算，导致通过给定代理节点获取的一个服务器cookie可验证该节点后的每个PROXYv2声明源，路
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 1.18.0 ~ 1.25.2 -

II. Public POCs for CVE-2026-54478

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III. Intelligence Information for CVE-2026-54478

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Vendor Advisories for CVE-2026-54478 (1)

Same Patch Batch · NLnet Labs · 2026-07-22 · 24 CVEs total

CVE-2026-55973 7.5 HIGH 'dns-error-reporting: yes' leads to stack buffer overflow
CVE-2026-32665 7.5 HIGH Remote DNS-over-QUIC denial of service due to `quic-size` budget bypass
CVE-2026-40691 7.5 HIGH Packet of death for DNSCrypt over TCP
CVE-2026-44690 7.5 HIGH Cross-zone wildcard cache poisoning via RRSIG.labels manipulation
CVE-2026-50248 6.5 MEDIUM BOGUS configured primary hostname accepted for XFR in auth/rpz zones
CVE-2026-55991 5.9 MEDIUM Remote DNS-over-QUIC (DoQ) flow-control assertion failure in libngtcp2
CVE-2026-14586 5.9 MEDIUM Assertion in libngtcp2 when under pressure in high concurrency DNS-over-QUIC environments
CVE-2026-56444 5.9 MEDIUM Degradation of resolution service when 'discard-timeout' and 'serve-expired-client-timeout
CVE-2026-44621 5.9 MEDIUM Libunbound applications configured with 'unwanted-reply-threshold' could eventually be abr
CVE-2026-55990 5.9 MEDIUM Packet of death for a DNSCrypt misconfigured Unbound
CVE-2026-50046 5.9 MEDIUM Possible heap use-after-free in an error path when a DoT forwarded query is jostled out
CVE-2026-55717 5.9 MEDIUM 'serve-expired-client-timeout' and 'response-ip' CNAME redirect could lead to a crash
CVE-2026-52863 5.9 MEDIUM Memory corruption could lead to crash and denial of service
CVE-2026-50045 5.3 MEDIUM 'max-global-quota' reset by DNSSEC validation restarts
CVE-2026-50251 5.3 MEDIUM Attacker supplied '0.0.0.0'/'::' glue triggers defensive full-cache flush
CVE-2026-56416 4.8 MEDIUM Possible heap buffer overflow when validator canonicalizes RDATA that contains domain name
CVE-2026-46582 3.7 LOW A wildcard replay, as another piece of data, triggers poisoning in the serve expired reply
CVE-2026-44687 3.7 LOW Off-by-one error in 'harden-below-nxdomain' logic can shadow a stub/forward zone by a legi
CVE-2026-41637 3.7 LOW Degradation of resolution service from improperly accounted client-terminated DNS-over-QUI
CVE-2026-42955 3.7 LOW Extra fix for CVE-2026-40622 to also clamp the TTL of A/AAAA records disallowing a one-tim

Showing top 20 of 24 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Unbound
Same vendor: NLnet Labs
Same weakness: CWE-290

V. Comments for CVE-2026-54478

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