CVE-2023-43622
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.
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 68.8%, higher than 99% of all known CVEs. Patch or mitigate before the next change window.
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.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 68.82% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-400
- Affected
- apache/http server
- Source
- security@apache.org
EPSS moved from 68.8% on 20 October 2026 to 68.8% on 3 November 2026. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”.
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
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.