CVE-2026-50243: In NLnet Labs Unbound 1.6.2 up to and including 1.25.1, when Unbound is configured with the 'respip' module in front of the validator together with a 'response-ip' redirect rule or
In NLnet Labs Unbound 1.6.2 up to and including 1.25.1, when Unbound is configured with the 'respip' module in front of the validator together with a 'response-ip' redirect rule or an RPZ file with an RPZ-IP trigger, the rewriting handler does not check the security status of the upstream answer and can instead rewrite a BOGUS A/AAAA answer to point to an operator's configured IP. If the validator finds an expired or otherwise invalid RRSIG on an answer whose A record falls within a 'response-ip'/RPZ configuration, the answer is still rewritten and given a hard coded security level of INSECURE. This results in the client receiving an INSECURE NOERROR reply rewritten by the operator's configured IP. A malicious actor can exploit the possible poisonous effect by spoofing a BOGUS A/AAAA answer that falls inside the operator's configured subnet rewrites. Such DNSSEC protected answers are then insecurely redirected to the operator's configured target.
Details
Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-50243
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-502430.11% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 1% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-50243 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
Recent advisories for In NLnet Labs
A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.
- mediumCVE-2026-56444: In NLnet Labs Unbound 1.20.0 up to and including 1.25.1, when Unbound is configured with 'serv…nvd · 2026-07-22
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- mediumCVE-2026-55991: In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, a remote unauthenticated client can t…nvd · 2026-07-22
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- highCVE-2026-55973: In NLnet Labs Unbound 1.23.0 up to and including 1.25.1, when 'dns-error-reporting: yes' is se…nvd · 2026-07-22
- mediumCVE-2026-55717: In NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when 'serve-expired: yes' is set toge…nvd · 2026-07-22
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