CVE-2021-25214
Description
Incremental zone transfers (IXFR) provide a way of transferring changed portion(s) of a zone between servers. An IXFR stream containing SOA records with an owner name other than the transferred zone's apex may cause the receiving named server to inadvertently remove the SOA record for the zone in question from the zone database. This leads to an assertion failure when the next SOA refresh query for that zone is made.
Mitigation
Disabling incremental zone transfers (IXFR) by setting "request-ixfr no;" in the desired configuration block (options, zone, or server) prevents the failing assertion from being evaluated.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.5 | 6.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker that can trigger an assert statement can still lead to a denial of service if the relevant code can be triggered by an attacker, and if the scope of the assert() extends beyond the attacker's own session.
Acknowledgements
Red Hat would like to thank ISC for reporting this issue. Upstream acknowledges Greg Kuechle (SaskTel) as the original reporter.
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