CVE-2026-97206
DNS-over-QUIC (DoQ) path-migration can lead to use-after-free on multi-threaded deployments.
High 7.5
NLnet Labs Unbound, 1.22.0 up to and including version 1.26.1, contains a DNS-over-QUIC (DoQ) lifetime bug reachable by a remote DoQ client under multi-threaded operation. A client-triggered QUIC path migration can enter stream/connection cleanup while a mesh reply still retains a pointer to the DoQ stream. Cleanup frees the DoQ stream and when the pending mesh reply later completes it dereferences a stale pointer leading to a crash.
Assigner
NLnet Labs
NLnet Labs
Published
2026-10-21
2026-10-21
Updated
2026-10-21
2026-10-21
Reserved
2026-10-14
2026-10-14
Scores
| Source | CVSS | Score | Severity | Vector |
|---|---|---|---|---|
| NLnet Labs | 3.1 | 7.5 | High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Weaknesses
Affected
| Vendor | Product | Versions |
|---|---|---|
| NLnet Labs | Unbound | 1.22.0 to < 1.26.2 (affected)
others: unaffected |
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-97206.txt vendor-advisory
Full CVE JSON record (5.2)
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"value": "Kunta Chu (Tsinghua University)"
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"value": "NLnet Labs Unbound, 1.22.0 up to and including version 1.26.1, contains a DNS-over-QUIC (DoQ) lifetime bug reachable by a remote DoQ client under multi-threaded operation. A client-triggered QUIC path migration can enter stream/connection cleanup while a mesh reply still retains a pointer to the DoQ stream. Cleanup frees the DoQ stream and when the pending mesh reply later completes it dereferences a stale pointer leading to a crash."
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"value": "compiled with DNS-over-QUIC support"
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"problemTypes": [
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"descriptions": [
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"cweId": "CWE-416",
"description": "CWE-416: Use After Free",
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"solutions": [
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"value": "This issue is fixed starting with version 1.26.2"
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"time": "2026-09-20T00:00:00.000Z",
"value": "Issue reported by Kunta Chu"
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"time": "2026-09-29T00:00:00.000Z",
"value": "NLnet Labs shares patch"
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"time": "2026-09-30T00:00:00.000Z",
"value": "Kunta Chu verifies patch"
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"time": "2026-10-21T00:00:00.000Z",
"value": "Fixes released with version 1.26.2"
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"title": "DNS-over-QUIC (DoQ) path-migration can lead to use-after-free on multi-threaded deployments.",
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