# What is CVE-2023-50387?

> CVE-2023-50387 is a high-severity flaw (CVSS 7.5) in Windows Server 2012 from Microsoft, published on 14 February 2024. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at over 99%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2023-50387

## At a glance

- **Verdict:** Fix this soon. Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.
- **Precursor Intelligence risk score:** 71 out of 100 (High); action: Patch now. Kept up to date as the evidence changes.
- **Severity:** High (CVSS 7.5 out of 10)
- **Known to be exploited:** No, not on the list of flaws known to be exploited today
- **Chance of use in the next 30 days:** over 99% (latest exploit-likelihood forecast)
- **Published:** 14 February 2024
- **Record last updated:** 17 June 2026
- **Main product:** Windows Server 2012 from Microsoft
- **Affected products:** 13

## What is CVE-2023-50387? In plain terms

It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can take it offline.

### The official 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.

### What kind of flaw is it?

- CWE-770: Allocation of Resources Without Limits or Throttling

### How an attack on it works

- Where an attacker can be: Anywhere on the internet
- How hard it is to pull off: Easy: no special conditions
- Login needed first: No login needed
- Does someone have to click: No, nobody has to do anything
- What an attacker gets: Can take it offline

Severity vector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`

## Is CVE-2023-50387 being exploited? Not that we know of

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at over 99%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: >99%, >99%, >99%, >99%, >99%, >99%, >99%.

### Timeline

- 14 February 2024: Published
- 11 June 2025: Exploit likelihood jumped
- 2 July 2025: Exploit likelihood fell
- 17 June 2026: Record last updated

### How Precursor Intelligence ranks it

CVE-2023-50387 scores **71 out of 100 (High)**, with the action "Patch now".

Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less:

- Evidence it is being exploited: biggest factor
- How severe it is: strong factor
- How widely exposed it is: smaller factor
- Threat activity around it: smaller factor

85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it.

## Who is affected by CVE-2023-50387?

The published record lists 13 products. Versions are as published: "4.8.0 to before 4.8.6" means from 4.8.0 up to, but not including, 4.8.6.

- [Windows Server 2012](https://www.precursorintelligence.com/product/microsoft/windows_server_2012) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): r2
- [Enterprise Linux](https://www.precursorintelligence.com/product/redhat/enterprise_linux) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 6.0, 7.0, 8.0, 9.0
- [Bind](https://www.precursorintelligence.com/product/isc/bind) by [Isc](https://www.precursorintelligence.com/vendors/isc) (Application): 9.0.0 to 9.16.46, 9.18.0 to 9.18.22, 9.19.0 to 9.19.20
- [Recursor](https://www.precursorintelligence.com/product/powerdns/recursor) by [Powerdns](https://www.precursorintelligence.com/vendors/powerdns) (Application): 4.8.0 to before 4.8.6, 4.9.0 to before 4.9.3, 5.0.0 to before 5.0.2
- [Dnsmasq](https://www.precursorintelligence.com/product/thekelleys/dnsmasq) by [Thekelleys](https://www.precursorintelligence.com/vendors/thekelleys) (Application): before 2.90
- [Fedora](https://www.precursorintelligence.com/product/fedoraproject/fedora) by [Fedoraproject](https://www.precursorintelligence.com/vendors/fedoraproject) (Operating system): 39
- [Knot Resolver](https://www.precursorintelligence.com/product/nic/knot_resolver) by [Nic](https://www.precursorintelligence.com/vendors/nic) (Application): before 5.71
- [Unbound](https://www.precursorintelligence.com/product/nlnetlabs/unbound) by [Nlnetlabs](https://www.precursorintelligence.com/vendors/nlnetlabs) (Application): before 1.19.1
- [Windows Server 2008](https://www.precursorintelligence.com/product/microsoft/windows_server_2008) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): r2-sp1
- [Windows Server 2016](https://www.precursorintelligence.com/product/microsoft/windows_server_2016) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified
- [Windows Server 2019](https://www.precursorintelligence.com/product/microsoft/windows_server_2019) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified
- [Windows Server 2022](https://www.precursorintelligence.com/product/microsoft/windows_server_2022) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified
- [Windows Server 2022 23H2](https://www.precursorintelligence.com/product/microsoft/windows_server_2022_23h2) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified

## How do I fix CVE-2023-50387?

1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list.
2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisories and patch notes first in the list.
3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in.
4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood.

### References

- [gitlab.nic.cz](https://gitlab.nic.cz/knot/knot-resolver/-/releases/v5.7.1) (Patch)
- [msrc.microsoft.com](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-50387) (Patch, Vendor advisory)
- [theregister.com](https://www.theregister.com/2024/02/13/dnssec_vulnerability_internet/) (Patch, Third-party advisory)
- [nlnetlabs.nl](https://nlnetlabs.nl/news/2024/Feb/13/unbound-1.19.1-released/) (Vendor advisory)
- [openwall.com](http://www.openwall.com/lists/oss-security/2024/02/16/2) (Mailing list)
- [openwall.com](http://www.openwall.com/lists/oss-security/2024/02/16/3) (Mailing list)
- [access.redhat.com](https://access.redhat.com/security/cve/CVE-2023-50387) (Third-party advisory)
- [bugzilla.suse.com](https://bugzilla.suse.com/show_bug.cgi?id=1219823) (Issue tracking)
- [docs.powerdns.com](https://docs.powerdns.com/recursor/security-advisories/powerdns-advisory-2024-01.html) (Third-party advisory)
- [kb.isc.org](https://kb.isc.org/docs/cve-2023-50387) (Third-party advisory, Vulnerability database)
- [lists.debian.org](https://lists.debian.org/debian-lts-announce/2024/02/msg00006.html)
- [lists.debian.org](https://lists.debian.org/debian-lts-announce/2024/05/msg00011.html)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6FV5O347JTX7P5OZA6NGO4MKTXRXMKOZ/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BUIP7T7Z4T3UHLXFWG6XIVDP4GYPD3AI/) (Mailing list)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HVRDSJVZKMCXKKPP6PNR62T7RWZ3YSDZ/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IGSLGKUAQTW5JPPZCMF5YPEYALLRUZZ6/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PNNHZSZPG2E7NBMBNYPGHCFI4V4XRWNQ/) (Mailing list)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RGS7JN6FZXUSTC2XKQHH27574XOULYYJ/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SVYA42BLXUCIDLD35YIJPJSHDIADNYMP/) (Mailing list)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TEXGOYGW7DBS3N2QSSQONZ4ENIRQEAPG/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UQESRWMJCF4JEYJEAKLRM6CT55GLJAB7/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZDZFMEKQTZ4L7RY46FCENWFB5MDT263R/)
- [lists.thekelleys.org.uk](https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2024q1/017430.html) (Mailing list, Third-party advisory)
- [news.ycombinator.com](https://news.ycombinator.com/item?id=39367411) (Third-party advisory)
- [news.ycombinator.com](https://news.ycombinator.com/item?id=39372384) (Issue tracking)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20240307-0007/)
- [athene-center.de](https://www.athene-center.de/aktuelles/key-trap) (Third-party advisory)
- [athene-center.de](https://www.athene-center.de/fileadmin/content/PDF/Technical_Report_KeyTrap.pdf) (Technical description, Third-party advisory)
- [isc.org](https://www.isc.org/blogs/2024-bind-security-release/) (Third-party advisory)
- [securityweek.com](https://www.securityweek.com/keytrap-dns-attack-could-disable-large-parts-of-internet-researchers/) (Press/media coverage, Third-party advisory)
- [lists.debian.org](https://lists.debian.org/debian-lts-announce/2024/09/msg00001.html)
- [lists.debian.org](https://lists.debian.org/debian-lts-announce/2024/11/msg00035.html)

## Questions

### What is CVE-2023-50387?

CVE-2023-50387 is a high-severity flaw in Windows Server 2012 from Microsoft, published on 14 February 2024. It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can take it offline.

### How serious is CVE-2023-50387?

It scores 7.5 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2023-50387 is 71 out of 100, which is High. Its action is "Patch now". Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.

### Is CVE-2023-50387 being exploited?

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at over 99%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2023-50387 affect?

For Windows Server 2012 from Microsoft: r2. The record lists 13 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2023-50387?

Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet.

## Does CVE-2023-50387 affect you?

Precursor Intelligence keeps checking for you:

- **Tell us what you run.** Pick your software from a list, or let us work it out from your website.
- **We match it to every flaw.** Over 400,000 published flaws, checked against your list.
- **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it.
- **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools.

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