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CVE-2026-52863— Memory corruption could lead to crash and denial of service

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 1.25.0版本至1.25.1版本存在资源管理错误漏洞，该漏洞源于respip和dns64模块协作时创建了视图名称的浅拷贝，可能导致在压力环境下原视图名称所有者被驱逐时发生内存损坏。

CVSS 5.9 · Medium EPSS 0.26% · P18

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
NLnet Labs Unbound 1.25.0< 1.25.2 affected
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I. Basic Information for CVE-2026-52863

Vulnerability Information
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Vulnerability Title
Memory corruption could lead to crash and denial of service
Source: CVE Program / CVE List V5
Vulnerability Description
In NLnet Labs Unbound 1.25.0 up to and including 1.25.1, a fix that makes the 'respip' and 'dns64' modules work together, creates a shallow copy of the view name in effect that could lead to memory corruption if the owner of the original view name is jostled out when Unbound is under pressure. Unbound needs to be configured with one of 'respip'/'rpz' modules, together with a module that can attach subqueries (respip CNAME redirection, dns64, subnetcache) and a configured 'access-control-view' while Unbound is under pressure so that joslte logic kicks in and starts dropping slow queries. The subquery is getting a shallow copy of the view name and if the super query which owns the view name is jostled out, memory corruption can occur. Likelihood of a crash is low, since it relies heavily on the underlying memory allocator and the memory layout. Debug memory builds (e.g., ASAN) that catch the free terminate the server.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
释放后使用
Source: CVE Program / CVE List V5
Vulnerability Title
NLnet Labs Unbound 资源管理错误漏洞
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 1.25.0版本至1.25.1版本存在资源管理错误漏洞，该漏洞源于respip和dns64模块协作时创建了视图名称的浅拷贝，可能导致在压力环境下原视图名称所有者被驱逐时发生内存损坏。
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 1.25.0 ~ 1.25.2 -

II. Public POCs for CVE-2026-52863

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III. Intelligence Information for CVE-2026-52863

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Patches & Fixes for CVE-2026-52863 (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-2026-55717 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-416

V. Comments for CVE-2026-52863

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