EUVD-2026-80770
GHSA-vrwj-p746-fr2r
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Remote unauthenticated attacker-influenced DNS response, low complexity, availability-only impact (memory-leak DoS) with no confidentiality or integrity effect; scope unchanged.
Primary rating from Vendor (isc).
CVSS VectorNVD
Lifecycle Timeline
2DescriptionNVD
A BIND resolver encountering an SVCB/HTTPS AliasMode record referencing 14 or more SVCB/HTTPS ServiceMode records may fail to properly deallocate internal resources. If this happens repeatedly, resource exhaustion will eventually prevent the resolver from performing new recursive lookups. This issue affects BIND 9 versions 9.18.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.18.11-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.
AnalysisAI
Resource exhaustion in ISC BIND 9 recursive resolvers allows unauthenticated remote attackers to cause a denial of service by repeatedly triggering a memory leak through crafted SVCB/HTTPS AliasMode records that reference 14 or more ServiceMode records. Affected versions include 9.18.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, and corresponding -S1 subscription builds; patched versions are 9.20.29 and 9.21.26. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires the BIND 9 recursive resolver to process an SVCB/HTTPS AliasMode record that references 14 or more SVCB/HTTPS ServiceMode records - meaning the attacker must control or influence the DNS response (a malicious/attacker-operated authoritative zone) and must repeatedly cause the resolver to resolve such records, since a single occurrence only leaks resources and exhaustion accumulates over many repetitions. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a genuine, well-calibrated availability risk. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Vendor-released patch: upgrade to BIND 9.20.29 or 9.21.26 (or corresponding -S1 builds) as provided by ISC; these are the fixed versions referenced in the advisory. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory every BIND 9 deployment and flag those running 9.18.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, and the corresponding -S1 subscription builds, then enable monitoring with alerting on resolver memory growth and elevated SERVFAIL or query-timeout rates so early exhaustion is detected rather than discovered as an outage. …
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Same weakness CWE-401 – Memory Leak
View allSame technique Denial Of Service
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External POC / Exploit Code
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