Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1336 CNY

100%
Buy Us a Coffee

CVE-2026-32665— Remote DNS-over-QUIC denial of service due to `quic-size` budget bypass

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 1.22.0版本至1.25.1之前版本存在输入验证错误漏洞，该漏洞源于下游DNS-over-QUIC实现中，每个流的大小门限被绕过，大输入缓冲区仅在从初始流接收到2字节长度前缀后才分配，可能导致远程客户端使用低成本输入使Unbound超过配置的大小限制，造成拒绝服务。

CVSS 7.5 · High EPSS 0.29% · P21

Affected Version Matrix 1

VendorProduct Version RangeStatus
NLnet Labs Unbound 1.22.0< 1.25.2 affected
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-32665

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
Remote DNS-over-QUIC denial of service due to `quic-size` budget bypass
Source: CVE Program / CVE List V5
Vulnerability Description
In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, when downstream DNS-over-QUIC (DoQ) is enabled, the first two bidirectional streams on a new QUIC connection (stream_id 0 and 4) bypass the per-stream 'quic-size' gate entirely, and large input buffers are allocated later, after only the 2-byte length prefix has been received from the initial streams. As a result, a remote client can make Unbound exceed the configured 'quic-size' limit with low-cost input. Using only one connection and two streams, each sending a declared 65535-byte length prefix and then holding the streams open, a client can already trivially make Unbound roughly allocate double that amount. This is a remote availability issue / memory-accounting bypass in the downstream DoQ implementation that leads to denial of service for new DoQ clients. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1284
Source: CVE Program / CVE List V5
Vulnerability Title
NLnet Labs Unbound 输入验证错误漏洞
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 1.22.0版本至1.25.1之前版本存在输入验证错误漏洞，该漏洞源于下游DNS-over-QUIC实现中，每个流的大小门限被绕过，大输入缓冲区仅在从初始流接收到2字节长度前缀后才分配，可能导致远程客户端使用低成本输入使Unbound超过配置的大小限制，造成拒绝服务。
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 1.22.0 ~ 1.25.2 -

II. Public POCs for CVE-2026-32665

# POC Description Source Link Shenlong Link
AI-Generated POC Premium

No public POC found.

Login to generate AI POC

III. Intelligence Information for CVE-2026-32665

请登录查看更多情报信息。

Vendor Advisories for CVE-2026-32665 (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-2026-40691 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-2026-52863 5.9 MEDIUM Memory corruption could lead to crash and denial of service
CVE-2026-55717 5.9 MEDIUM 'serve-expired-client-timeout' and 'response-ip' CNAME redirect could lead to a crash
CVE-2026-55991 5.9 MEDIUM Remote DNS-over-QUIC (DoQ) flow-control assertion failure in libngtcp2
CVE-2026-50046 5.9 MEDIUM Possible heap use-after-free in an error path when a DoT forwarded query is jostled out
CVE-2026-55990 5.9 MEDIUM Packet of death for a DNSCrypt misconfigured Unbound
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-2026-14586 5.9 MEDIUM Assertion in libngtcp2 when under pressure in high concurrency DNS-over-QUIC environments
CVE-2026-50251 5.3 MEDIUM Attacker supplied '0.0.0.0'/'::' glue triggers defensive full-cache flush
CVE-2026-50045 5.3 MEDIUM 'max-global-quota' reset by DNSSEC validation restarts
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-2026-54478 3.7 LOW DNS Cookie bypass when combined with proxy-protocol use
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-1284

V. Comments for CVE-2026-32665

No comments yet

Leave a comment