CVE-2023-43622

Name: CVE-2023-43622
Creator: NVD / NIST
Published: 2023-10-23T07:15:11.243+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 70.59%

Last modified Jun 17, 2026

CVE-2023-43622 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. An attacker, opening a HTTP/2 connection with an initial window size of 0, was able to block handling of that connection indefinitely in Apache HTTP Server. This could be used to exhaust worker resources in the server, similar to the well known "slow loris" attack pattern. This has been fixed in version 2.4.58, so that such connection are terminated properly after the configured connection timeout. This issue affects Apache HTTP Server: from 2.4.55 through 2.4.57. Users are recommended to upgrade to version 2.4.58, which fixes the issue.. EPSS estimates a 70.59% chance of exploitation in the next 30 days.

Description

An attacker, opening a HTTP/2 connection with an initial window size of 0, was able to block handling of that connection indefinitely in Apache HTTP Server. This could be used to exhaust worker resources in the server, similar to the well known "slow loris" attack pattern. This has been fixed in version 2.4.58, so that such connection are terminated properly after the configured connection timeout. This issue affects Apache HTTP Server: from 2.4.55 through 2.4.57. Users are recommended to upgrade to version 2.4.58, which fixes the issue.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

70.59%

99.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-400

Affected Software

Vendor	Product	Versions
Apache	Http Server	>= 2.4.55, < 2.4.58

References

https://httpd.apache.org/security/vulnerabilities_24.htmlVendor Advisory
https://security.netapp.com/advisory/ntap-20231027-0011/Third Party Advisory
https://httpd.apache.org/security/vulnerabilities_24.htmlVendor Advisory
https://security.netapp.com/advisory/ntap-20231027-0011/Third Party Advisory

Timeline

Published: Oct 23, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-43622?

How severe is CVE-2023-43622?

CVE-2023-43622 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 70.59% probability of exploitation in the next 30 days.

How do I fix CVE-2023-43622?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2023-43622?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST