NLnet Labs Unbound up to 1.26.0 heap-based overflow

Summaryinfo

A vulnerability described as very critical has been identified in NLnet Labs Unbound up to 1.26.0. This affects an unknown function. Such manipulation leads to heap-based overflow. This vulnerability is listed as CVE-2026-82717. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as very critical, has been found in NLnet Labs Unbound up to 1.26.0. Affected by this issue is an unknown code block. The manipulation with an unknown input leads to a heap-based overflow vulnerability. Using CWE to declare the problem leads to CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at nlnetlabs.nl. This vulnerability is handled as CVE-2026-82717 since 09/07/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/16/2026).

Upgrading to version 1.26.1 eliminates this vulnerability.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Vendor

• NLnet Labs

Name

• Unbound

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20
• 1.21
• 1.22
• 1.23
• 1.24
• 1.25
• 1.26.0

CPE 2.3info

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CPE 2.2info

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Entryinfo

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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