How severe is CVE-2023-43622?

CVE-2023-43622 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2023-43622 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 71% (99th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-43622?

CVE-2023-43622 affects Apache Http Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2023-43622?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2023-43622 published?

CVE-2023-43622 was published on 2023-10-23 and last updated on 2026-06-17.

CVE-2023-43622

CVE-2023-43622 is a high-severity vulnerability in Apache Http Server with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 71% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-400.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 71% (99th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-400
Affected product: Apache Http Server
Published: 2023-10-23
Last modified: 2026-06-17

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.

Frequently asked questions

What is 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. 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.
How severe is CVE-2023-43622?: CVE-2023-43622 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2023-43622 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 71% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-43622?: CVE-2023-43622 affects Apache Http Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2023-43622?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2023-43622 published?: CVE-2023-43622 was published on 2023-10-23 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:*

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Threat intelligence

Threat-intel indicators referencing this CVE:

117.247.23.131 (ipv4-addr)
103.38.182.49 (ipv4-addr)
189.217.130.86 (ipv4-addr)
157.92.145.135 (ipv4-addr)
103.216.145.2 (ipv4-addr)
109.236.86.20 (ipv4-addr)
107.173.122.15 (ipv4-addr)