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HIGH severity

CVE-2023-50387 — unbound

HIGH

CVE-2023-50387 is a high-severity (CVSS 7.5) CWE-770 vulnerability. 2 public exploit references exist, so weaponization risk is real. A fix is available — see the affected versions and patch details below.

Published
Updated
Affected
13 products
Patched
See advisory
Exploits
2 known
Exploitation data as of Oct 28, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2023-50387.

EPSS Exploitation Probability

via FIRST.org ↗
100.0%probability of exploitation in next 30 days
Very High Risk-0.00%
Lower risk than most CVEs100th percentile — riskier than 100% of all scored CVEsHighest risk
37.6%58.4%79.2%100.0%52.0%100.0%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2023-50387 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 397,508 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.

Description

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 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.

Affected Products

13 products · 21 configurations
OS
fedorafedoraproject
1 version
39
Application
bindisc
≥ 9.19.0 && ≤ 9.19.20
range
OS
windows server 2008microsoft
1 version
r2
OS
windows server 2012microsoft
1 version
r2
OS
windows server 2016microsoft
all
OS
windows server 2019microsoft
all
Exploits & PoCs
2

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Certain DNSSEC aspects of the DNS protocol (in RFC 4033, 4034, 4035, 684…

github.comGithubFeb 2024

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Fix

    Upgrade the affected component to the fixed release for CVE-2023-50387, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

This vulnerability in DNSSEC-validating resolvers is of important severity because it can lead to uncontrolled CPU consumption, resulting in a Denial of Service (DoS). By exploiting this flaw, attackers can send specially crafted DNS responses that cause the resolver to enter a state of excessive resource utilization.…

Workaround published by Red Hat
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Source: Red Hat security advisory for CVE-2023-50387 (CC BY 4.0)
ProductFixed inAdvisory
Red Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSIONbind-32:9.8.2-0.68.rc1.el6_10.14RHSA-2025:0039
Red Hat Enterprise Linux 7bind-32:9.11.4-26.P2.el7_9.16RHSA-2024:3741
Red Hat Enterprise Linux 7 Extended Lifecycle Supportunbound-0:1.6.6-5.el7_9.1RHSA-2024:11003
Red Hat Enterprise Linux 8unbound-0:1.16.2-5.el8_9.2RHSA-2024:0965
Red Hat Enterprise Linux 8dnsmasq-0:2.79-31.el8_9.2RHSA-2024:1335
Red Hat Enterprise Linux 8bind9.16-32:9.16.23-0.16.el8_9.2RHSA-2024:1781
Red Hat Enterprise Linux 8bind-32:9.11.36-11.el8_9.1RHSA-2024:1782
Red Hat Enterprise Linux 8bind-32:9.11.36-14.el8_10RHSA-2024:3271

Frequently Asked Questions

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 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.
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CVE-2023-50387: unbound DoS (High 7.5)