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Fencer Vulns
high 7.5

CVE-2023-43622 in the critical feed json

Apache HTTP Server: DoS in HTTP/2 with initial windows size 0

published 2023-10-23 3 y ago modified 2026-09-08 2 mo ago also BIT-apache-2023-43622 , EUVD-2023-48022

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
68.8%
EPSS 68.8% chance of exploitation in 30 days, percentile 99.3%
public exploits
0
none known

Summary

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.

Patch / fix

  • bitnami apache 2.4.58
  • apache http_server 2.4.58
  • apache2 Debian 12 2.4.59-1~deb12u1
  • apache2 Debian 14, Debian 13 2.4.58-1

debian advisories DEBIAN-CVE-2023-43622

  • mod_http2 RHEL 9 2.0.26-1.el9

red hat advisories RHSA-2024:2368

  • apache2 openSUSE Tumbleweed 2.4.58-1.1

opensuse advisories openSUSE-SU-2024:13350-1

  • mod_http2 AlmaLinux 9 2.0.26-1.el9

almalinux advisories ALSA-2024:2368

  • apache2 Alpine 3.24, Alpine 3.23, Alpine 3.22 +7 more 2.4.58-r0

alpine advisories ALPINE-CVE-2023-43622

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • httpd CBL-Mariner 2.0 2.4.58-1
  • mod_http2 Azure Linux 3.0 2.0.29-3

azure linux advisories AZL-31610AZL-44955

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2023-43622 updated cvss 7.5

httpd: mod_http2: DoS in HTTP/2 with initial window size 0

  • Red Hat Enterprise Linux AppStream (v. 9) mod_http2 2.0.26-1.el9
    fixed: vendor fix RHSA-2024:2368
  • Red Hat Enterprise Linux 8 mod_http2 Red Hat JBoss Core Services mod_http2
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-25-133-01 updated cvss 7.5

Hitachi Energy Service Suite

  • Hitachi Energy Service Suite <=9.8.1.3
    affected: fixed in 9.8.1.4
  • Hitachi Energy Service Suite 9.8.1.4
    fixed

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
2 y ago

Exploit prediction

68.82% chance of exploitation in the next 30 days, higher than 99.3% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
bitnami apache
>=2.4.55, <2.4.58
2.4.58

Affected products

  • Apache Software Foundation Apache HTTP Server

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.