CVE-2026-55717

See a problem?
Please try reporting it to the source first.
Source
https://cve.org/CVERecord?id=CVE-2026-55717
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55717.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-55717
Downstream
Related
Published
2026-07-22T14:17:21Z
Modified
2026-09-10T18:26:55Z
Severity
  • 5.9 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
Summary
[none]
Details

In NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when 'serve-expired: yes' is set together with a 'response-ip: redirect' /'response-ip-data: CNAME ' rule (or the RPZ 'rpz-cname-override' equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the second pass it resets 'alias_rrset' but not 'partial_rep'. Later, this inconsistency leads to a NULL pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By delaying the answer when the previous record has expired, the vulnerable path of 'serve-expired-client-timeout' is taken leading to denial of service via the server crash.

References

Affected packages

Git / github.com/nlnetlabs/unbound

Affected ranges

Type
GIT
Repo
https://github.com/nlnetlabs/unbound
Events
Introduced
6e7717986b25a48952ebb18e131d6eaa005a9757
Fixed
c33ad1b1a21e48bfe4f140e90252a9be1b0c5745
Database specific
Show details 
{
    "cpe": "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*",
    "extracted_events": [
        {
            "introduced": "1.10.0"
        },
        {
            "fixed": "1.25.2"
        }
    ],
    "source": "CPE_RANGE"
}

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55717.json"