CVE-2026-42959— Crash during DNSSEC validation of malicious content
Possible ATT&CK Techniques 1AI
T1498.002 · Reflection AmplificationAffected Version Matrix 1
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| NLnet Labs | Unbound | < 1.25.1 | affected |
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I. Basic Information for CVE-2026-42959
Vulnerability Information
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Vulnerability Title
Crash during DNSSEC validation of malicious content
Source: NVD (National Vulnerability Database)
Vulnerability Description
NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets.
Source: NVD (National Vulnerability Database)
CVSS Information
N/A
Source: NVD (National Vulnerability Database)
Vulnerability Type
使用未经初始化的指针
Source: NVD (National Vulnerability Database)
Vulnerability Title
NLnet Labs Unbound 缓冲区错误漏洞
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 1.25.0及之前版本存在缓冲区错误漏洞，该漏洞源于DNSSEC验证器中使用错误计数器计算写入偏移量，导致未初始化指针被引用，可能造成进程崩溃。
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 | 0 ~ 1.25.1 | - |
II. Public POCs for CVE-2026-42959
| # | POC Description | Source Link | Shenlong Link |
|---|
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Vendor Advisories for CVE-2026-42959 (1)
Same Patch Batch · NLnet Labs · 2026-05-20 · 11 CVEs total
| CVE-2026-41292 | Long list of incoming EDNS options degrades performance | |
| CVE-2026-42923 | Degradation of service with unbounded NSEC3 hash calculations | |
| CVE-2026-42944 | Heap overflow with multiple NSID, COOKIE, PADDING EDNS options | |
| CVE-2026-42960 | Possible cache poisoning via promiscuous records for the authority section | |
| CVE-2026-42534 | Jostle logic bypass degrades resolution performance | |
| CVE-2026-32792 | Packet of death with DNSCrypt | |
| CVE-2026-40622 | Another 'ghost domain names' attack variant | |
| CVE-2026-44390 | Unbounded name compression in certain cases causes degradation of service | |
| CVE-2026-44608 | Use after free and crash under special conditions in RPZ code | |
| CVE-2026-33278 | Possible arbitrary code execution during DNSSEC validation |
IV. Related Vulnerabilities
Same product: Unbound
- CVE-2026-44608
Use after free and crash under special conditions in RPZ cod - CVE-2026-44390
Unbounded name compression in certain cases causes degradati - CVE-2026-42960
Possible cache poisoning via promiscuous records for the aut - CVE-2026-42944
Heap overflow with multiple NSID, COOKIE, PADDING EDNS optio - CVE-2026-42923
Degradation of service with unbounded NSEC3 hash calculation
Same vendor: NLnet Labs
- CVE-2026-44608
Use after free and crash under special conditions in RPZ cod - CVE-2026-44390
Unbounded name compression in certain cases causes degradati - CVE-2026-42960
Possible cache poisoning via promiscuous records for the aut - CVE-2026-42944
Heap overflow with multiple NSID, COOKIE, PADDING EDNS optio - CVE-2026-42923
Degradation of service with unbounded NSEC3 hash calculation
V. Comments for CVE-2026-42959
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