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CVE-2026-33278— Possible arbitrary code execution during DNSSEC validation

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 1.19.1版本至1.25.0版本存在资源管理错误漏洞，该漏洞源于DNSSEC验证器中深度复制数据结构时错误覆盖目标指针，可能导致拒绝服务和可能的远程代码执行。攻击者可通过控制恶意签名区域并查询易受攻击的Unbound利用此漏洞。

CVSS 9.1 · Critical EPSS 1.13% · P65

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
NLnet Labs Unbound 1.19.1< 1.25.1 affected
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I. Basic Information for CVE-2026-33278

Vulnerability Information
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Vulnerability Title
Possible arbitrary code execution during DNSSEC validation
Source: CVE Program / CVE List V5
Vulnerability Description
NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep-copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination's pointer with the source's pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/U:Red
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NLnet Labs开源的一个高性能DNS解析器。 NLnet Labs Unbound 1.19.1版本至1.25.0版本存在资源管理错误漏洞，该漏洞源于DNSSEC验证器中深度复制数据结构时错误覆盖目标指针，可能导致拒绝服务和可能的远程代码执行。攻击者可通过控制恶意签名区域并查询易受攻击的Unbound利用此漏洞。
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 1.19.1 ~ 1.25.1 -

II. Public POCs for CVE-2026-33278

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III. Intelligence Information for CVE-2026-33278

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Vendor Advisories for CVE-2026-33278 (1)

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

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-2026-40622 Another 'ghost domain names' attack variant
CVE-2026-44608 Use after free and crash under special conditions in RPZ code

IV. Related Vulnerabilities

Same product: Unbound
Same vendor: NLnet Labs
Same weakness: CWE-416

V. Comments for CVE-2026-33278

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