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Vulnerability record · CVE-2026-82717 · published 16 September 2026

CVE-2026-82717: Nlnetlabs unbound heap-based buffer overflow vulnerability

Nlnetlabs · Unbound

In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in that can progressively corrupt heap memory and under certain systems and compilation options could lead to remote code execution. The vulnerability starts when CNAME synthesis during an upstream response needs to enforce(rewrite) a max TTL value in the packet buffer. Coupled with a compression pointer that points to the overwritten value and invalidates the domain name, it leads to an error path that does not properly move the buffer position and allows for the heap buffer overflow. Since this is heavily reliant on heap memory layout, results are memory corruption that eventually leads to a crash and under specific systems and compilation options remote code execution.

8.4 CVSS 4.0 High EPSS 0.78% · top 45.8% CWE-122 · Heap-based buffer overflow
8.4CVSS 4.0 base score
0.78%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
1References
23 Sep 2026Last modified by NVD

Description

In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in that can progressively corrupt heap memory and under certain systems and compilation options could lead to remote code execution. The vulnerability starts when CNAME synthesis during an upstream response needs to enforce(rewrite) a max TTL value in the packet buffer. Coupled with a compression pointer that points to the overwritten value and invalidates the domain name, it leads to an error path that does not properly move the buffer position and allows for the heap buffer overflow. Since this is heavily reliant on heap memory layout, results are memory corruption that eventually leads to a crash and under specific systems and compilation options remote code execution.

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-82717.txt PatchVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2019-25032Nlnetlabs unbound integer overflow vulnerabilityUnbound before 1.9.5 allows an integer overflow in the regional allocator via regional_alloc. NOTE: The vendor disputes that this is a vulnerability.…EPSS 2.2%9.8CVE-2019-25033Nlnetlabs unbound integer overflow vulnerabilityUnbound before 1.9.5 allows an integer overflow in the regional allocator via the ALIGN_UP macro. NOTE: The vendor disputes that this is a vulnerabil…EPSS 1.8%9.8CVE-2019-25034Nlnetlabs unbound integer overflow vulnerabilityUnbound before 1.9.5 allows an integer overflow in sldns_str2wire_dname_buf_origin, leading to an out-of-bounds write. NOTE: The vendor disputes that…EPSS 2.0%9.8CVE-2019-25035Nlnetlabs unbound out-of-bounds write vulnerabilityUnbound before 1.9.5 allows an out-of-bounds write in sldns_bget_token_par. NOTE: The vendor disputes that this is a vulnerability. Although the code…EPSS 2.0%9.8CVE-2019-25038Nlnetlabs unbound integer overflow vulnerabilityUnbound before 1.9.5 allows an integer overflow in a size calculation in dnscrypt/dnscrypt.c. NOTE: The vendor disputes that this is a vulnerability.…EPSS 2.0%9.8CVE-2019-25039Nlnetlabs unbound integer overflow vulnerabilityUnbound before 1.9.5 allows an integer overflow in a size calculation in respip/respip.c. NOTE: The vendor disputes that this is a vulnerability. Alt…EPSS 2.0%9.8CVE-2019-25042Nlnetlabs unbound out-of-bounds write vulnerabilityUnbound before 1.9.5 allows an out-of-bounds write via a compressed name in rdata_copy. NOTE: The vendor disputes that this is a vulnerability. Altho…EPSS 2.0%9.1CVE-2026-81642Nlnetlabs unbound heap-based buffer overflow vulnerabilityIn NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in the DNSSEC validator that enables denial of service and possible remot…EPSS 0.96%

Source: NIST National Vulnerability Database (record CVE-2026-82717), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.