CVE-2021-44790 | Possible buffer overflow when parsing multipart content in mod_lua of Apache HTTP Server 2.4.51 and earlier

Exp

A carefully crafted request body can cause a buffer overflow in the mod_lua multipart parser (r:parsebody() called from Lua scripts). The Apache httpd team is not aware of an exploit for the vulnerabilty though it might be possible to craft one. This issue affects Apache HTTP Server 2.4.51 and earlier.

Published: 2021-12-20 Last update: 2025-05-01 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-44790 is rated High Exploit Risk (89.2/100): CVSS Critical severity, with high exploitation likelihood (EPSS 86.23%, 99th percentile). 2 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-44790

EDB-ID Source Kind Published Link
51193 exploit_db edb 2023-04-01 Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-44790

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-29 86.01% 86.23% +0.22%
2 2026-04-10 87.09% 86.01% -1.08%
3 2026-03-04 — 87.09% —

Full EPSS history (95 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-44790

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
7.5 2.0 HIGH
AV:N/AC:L/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 6.4 [email protected]

Weakness enumeration for CVE-2021-44790

OS Trackers for CVE-2021-44790

vendor priority summary link
alpine — CVE-2021-44790: 1 source package rows (apache2); 8 state rows across 8 repos (3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 8, open 0. https://security.alpinelinux.org/vuln/CVE-2021-44790
debian not yet assigned CVE-2021-44790 not yet assigned priority: Debian including 1 source packages (apache2), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-44790
gentoo high CVE-2021-44790: 1 GLSA(s) (202208-20), 2 atom(s) (app-admin/apache-tools, www-servers/apache); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-44790
redhat high — https://access.redhat.com/security/cve/CVE-2021-44790
suse critical CVE-2021-44790 severity critical: SUSE including 300 source package names (amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, amazon/suse-sles-15-sp1-chost-byos-v20220127-hvm-ssd-x86_64, …), 509 product×package rows across 62 product lines (HPE Helion OpenStack 8, Image SLES15-SP3-EC2-HVM, … (62 product lines)): Fixed 262, Known Affected 231, Known Not Affected 16. https://www.suse.com/security/cve/CVE-2021-44790/
ubuntu medium CVE-2021-44790 medium priority: Ubuntu including 1 source packages (apache2), 8 status rows across 8 suites (bionic, focal, hirsute, impish, jammy, trusty, upstream, xenial): released 8. https://ubuntu.com/security/CVE-2021-44790

Affected software / configurations for CVE-2021-44790

Vendor Product Version Raw CPE
apache http_server < 2.4.52 cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
fedoraproject fedora 35 cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
fedoraproject fedora 36 cpe:2.3:o:fedoraproject:fedora:36:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
debian debian_linux 11.0 cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
tenable tenable.sc >= 5.16.0, < 5.20.0 cpe:2.3:a:tenable:tenable.sc:*:*:*:*:*:*:*:*
netapp cloud_backup — cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:*
oracle communications_element_manager <= 9.0 cpe:2.3:a:oracle:communications_element_manager:*:*:*:*:*:*:*:*
oracle communications_operations_monitor 4.3 cpe:2.3:a:oracle:communications_operations_monitor:4.3:*:*:*:*:*:*:*
oracle communications_operations_monitor 4.4 cpe:2.3:a:oracle:communications_operations_monitor:4.4:*:*:*:*:*:*:*
oracle communications_operations_monitor 5.0 cpe:2.3:a:oracle:communications_operations_monitor:5.0:*:*:*:*:*:*:*
oracle communications_session_report_manager <= 9.0 cpe:2.3:a:oracle:communications_session_report_manager:*:*:*:*:*:*:*:*
oracle communications_session_route_manager <= 9.0 cpe:2.3:a:oracle:communications_session_route_manager:*:*:*:*:*:*:*:*
oracle http_server 12.2.1.3.0 cpe:2.3:a:oracle:http_server:12.2.1.3.0:*:*:*:*:*:*:*
oracle http_server 12.2.1.4.0 cpe:2.3:a:oracle:http_server:12.2.1.4.0:*:*:*:*:*:*:*
oracle instantis_enterprisetrack 17.1 cpe:2.3:a:oracle:instantis_enterprisetrack:17.1:*:*:*:*:*:*:*
oracle instantis_enterprisetrack 17.2 cpe:2.3:a:oracle:instantis_enterprisetrack:17.2:*:*:*:*:*:*:*
oracle instantis_enterprisetrack 17.3 cpe:2.3:a:oracle:instantis_enterprisetrack:17.3:*:*:*:*:*:*:*
oracle zfs_storage_appliance_kit 8.8 cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2020-001:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-001:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-002:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-003:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-004:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-005:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-006:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-007:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-008:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2022-001:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2022-002:*:*:*:*:*:*
apple mac_os_x 10.15.7 cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2022-003:*:*:*:*:*:*
apple macos < 10.15.7 cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*
apple macos >= 11.0, < 11.6.6 cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*
apple macos >= 12.0, < 12.4 cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*

References for CVE-2021-44790

URL Tags
http://httpd.apache.org/security/vulnerabilities_24.html Vendor Advisory
http://packetstormsecurity.com/files/171631/Apache-2.4.x-Buffer-Overflow.html Exploit
http://seclists.org/fulldisclosure/2022/May/33 Mailing List Third Party Advisory
http://seclists.org/fulldisclosure/2022/May/35 Mailing List Third Party Advisory
http://seclists.org/fulldisclosure/2022/May/38 Mailing List Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/12/20/4 Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BFSWOH4X77CV7AH7C4RMHUBDWKQDL4YH/ Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RGWILBORT67SHMSLYSQZG2NMXGCMPUZO/ Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/X73C35MMMZGBVPQQCH7LQZUMYZNQA5FO/ Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Z7H26WJ6TPKNWV3QKY4BHKUKQVUTZJTD/ Third Party Advisory
https://security.gentoo.org/glsa/202208-20 Third Party Advisory
https://security.netapp.com/advisory/ntap-20211224-0001/ Third Party Advisory
https://support.apple.com/kb/HT213255 Third Party Advisory
https://support.apple.com/kb/HT213256 Third Party Advisory
https://support.apple.com/kb/HT213257 Third Party Advisory
https://www.debian.org/security/2022/dsa-5035 Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html Patch Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html Patch Third Party Advisory
https://www.tenable.com/security/tns-2022-01 Third Party Advisory
https://www.tenable.com/security/tns-2022-03 Third Party Advisory
cvelogic Threat Intelligence