{"id":"CVE-2026-82720","title":"NLnet Labs Unbound 1.12.0 up to and including 1.26.0 has a use-after-free vulnerability when compiled for DNS-over-HTTPs support with '--with-libnghttp2'","summary":"NLnet Labs Unbound 1.12.0 up to and including 1.26.0 has a use-after-free vulnerability when compiled for DNS-over-HTTPs support with '--with-libnghttp2'. During failure code paths (i.e., RPZ drop query, jostle due to heavy traffic), a d…","severity":"medium","cvss":5.9,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-416","CWE-825"],"vendor":"NLnet Labs","product":"Unbound","affected":["Unbound >= 1.12.0 < 1.26.1"],"published":"2026-09-16","updated":"2026-09-16","sourceUpdated":"2026-09-16T19:41:10.423","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-82720","references":[{"url":"https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-82720.txt","label":"sep@nlnetlabs.nl"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-82720.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-82720"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2535060"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-82720"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-82720"},{"url":"https://access.redhat.com/errata/RHSA-2026:68590"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-09-16T14:13:03.616721Z"},"ingestedAt":"2026-09-16T08:52:29.597Z","epss":0.00285,"epssPercentile":0.21201,"patched":["hardened_images"],"slug":"CVE-2026-82720","body":"## Overview\n\nNLnet Labs Unbound 1.12.0 up to and including 1.26.0 has a use-after-free vulnerability when compiled for DNS-over-HTTPs support with '--with-libnghttp2'. During failure code paths (i.e., RPZ drop query, jostle due to heavy traffic), a dropped DoH stream brings down the whole DoH session and does not account properly for other DoH streams in the same session. This leads to use-after-free in those code paths. If the prerequisites are satisfied (possible RPZ drop or heavy client traffic), a malicious actor can trigger the vulnerability with a single DoH connection and the appropriate traffic. Impact is limited as the reads are not user controlled and the use-after-free leads to early returns. However, a hardened allocator can catch the use-after-free and controllably terminate the process resulting to denial of service.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-82720.json)\n- **RHSA-2026:68590** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-17 · [advisory](https://access.redhat.com/errata/RHSA-2026:68590)","depth":"sunlit","depthScore":33,"depthScoreParts":{"impact":32.5,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}