CVE-2023-50387
Published: 14 February 2024
Summary
CVE-2023-50387 is a high-severity Allocation of Resources Without Limits or Throttling (CWE-770) vulnerability in Redhat Enterprise Linux. Its CVSS base score is 7.5 (High).
Operationally, ranked in the top 2.4% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
Deeper analysis
CVE-2023-50387 is a denial-of-service vulnerability in DNSSEC processing as defined in RFCs 4033, 4034, 4035, 6840 and related specifications. It stems from the requirement that validating resolvers evaluate every combination of DNSKEY and RRSIG records when a zone publishes many such records, resulting in excessive CPU consumption. The flaw, tracked as CWE-770 and nicknamed KeyTrap, affects any DNS resolver or authoritative server that implements the DNSSEC validation algorithm without additional safeguards.
An unauthenticated remote attacker can trigger the issue by sending one or more crafted DNSSEC responses that force the target to perform the full combinatorial evaluation. Successful exploitation produces sustained high CPU load and can render the resolver unresponsive, achieving a denial-of-service condition without any privileges or user interaction. The CVSS 3.1 base score of 7.5 reflects network attack vector, low complexity, and high availability impact.
Vendor advisories from Red Hat, SUSE, PowerDNS and coordinated lists on oss-security describe the problem and point to forthcoming patches or configuration work-arounds that limit the number of signatures or keys processed per response. The associated EPSS score rose from a low baseline to a peak of 0.5199 on 2026-03-20 before receding to the current value of 0.4321, indicating measurable post-disclosure exploitation interest that warrants renewed monitoring.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2023-55182
Vulnerability details
Certain DNSSEC aspects of the DNS protocol (in RFC 4033, 4034, 4035, 6840, and related RFCs) allow remote attackers to cause a denial of service (CPU consumption) via one or more DNSSEC responses, aka the "KeyTrap" issue. One of the…
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concerns is that, when there is a zone with many DNSKEY and RRSIG records, the protocol specification implies that an algorithm must evaluate all combinations of DNSKEY and RRSIG records.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
This control implements explicit throttling on session allocation, addressing the weakness of allocating resources without limits.
Plan testing exercises resource allocation limits and throttling during simulated failures, directly addressing weaknesses that allow unbounded resource use.
Contingency plan updates ensure recovery strategies address unbounded resource allocation, making it harder for attackers to exploit lack of throttling to cause prolonged outages.
Provides continuity when unbounded resource allocation at the primary site leads to exhaustion and downtime.
Alternate services allow operations to continue when primary allocation of resources lacks limits or throttling.
Explicit planning of security-related actions requires defining limits, windows, and resource allocations, making allocation without throttling far less likely.
Measures of performance include tracking allocation behavior and throttling effectiveness, reducing the window for resource exhaustion attacks.
Imposes an inactivity-based limit on network resource allocation, throttling the number of concurrently held connections.