What’s Vulnerable › Vulnerabilities

CVE-2021-44224: Possible NULL dereference or SSRF in forward proxy configurations in Apache HTTP Server 2.4.51 and earlier

• Severity: high (CVSS 8.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 82.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-12-20 · updated 2026-06-17
• Weakness: CWE-476

Description

A crafted URI sent to httpd configured as a forward proxy (ProxyRequests on) can cause a crash (NULL pointer dereference) or, for configurations mixing forward and reverse proxy declarations, can allow for requests to be directed to a declared Unix Domain Socket endpoint (Server Side Request Forgery). This issue affects Apache HTTP Server 2.4.7 up to 2.4.51 (included).

Affected products

• Apache HTTP Server: from 2.4.7 before 2.4.52 — fixed in 2.4.52
• macOS: 10.15.7, 10.15.7-security_update_2020-001, 10.15.7-security_update_2021-001, 10.15.7-security_update_2021-002, 10.15.7-security_update_2021-003, 10.15.7-security_update_2021-004 (+7)
• Apple macOS: before 10.15.7; from 11.0 before 11.6.6; from 12.0.0 before 12.4 — fixed in 10.15.7, 11.6.6, 12.4
• Debian Linux: 10.0, 11.0
• Fedoraproject Fedora: 34, 35, 36
• Oracle Communications Element Manager: before 9.0 — fixed in 9.0
• Oracle Corporation Communications Operations Monitor: 4.0, 4.3, 4.4, 5.0
• Oracle Communications Session Report Manager: before 9.0 — fixed in 9.0
• Oracle Communications Session Route Manager: before 9.0 — fixed in 9.0
• Oracle Corporation Oracle HTTP Server: 12.2.1.3.0, 12.2.1.4.0
• Oracle Instantis Enterprisetrack: 17.1, 17.2, 17.3
• Tenable.sc: from 5.14.0 before 5.20.0; from 5.16.0 before 202201.1 — fixed in 202201.1, 5.20.0

How to fix

Upgrade to a fixed version: Apache HTTP Server 2.4.52; Apple macOS 10.15.7, 11.6.6, 12.4; Oracle Communications Element Manager 9.0; Oracle Communications Session Report Manager 9.0; Oracle Communications Session Route Manager 9.0; Tenable.sc 202201.1, 5.20.0. Check the vendor advisory for mitigations.

References

• http://httpd.apache.org/security/vulnerabilities_24.html
• http://seclists.org/fulldisclosure/2022/May/33
• http://seclists.org/fulldisclosure/2022/May/35
• http://seclists.org/fulldisclosure/2022/May/38
• http://www.openwall.com/lists/oss-security/2021/12/20/3
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BFSWOH4X77CV7AH7C4RMHUBDWKQDL4YH/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RGWILBORT67SHMSLYSQZG2NMXGCMPUZO/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/X73C35MMMZGBVPQQCH7LQZUMYZNQA5FO/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Z7H26WJ6TPKNWV3QKY4BHKUKQVUTZJTD/
• https://security.gentoo.org/glsa/202208-20
• https://security.netapp.com/advisory/ntap-20211224-0001/
• https://support.apple.com/kb/HT213255

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