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NVD / CVE Program· CNA apache

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

CriticalCVSS 9.8 · v3.1—Proof of concept Fix available

Noroxi assessment

Priority: This week (action score 68/100)

  • Public proof-of-concept code exists (Exploit-DB, GitHub); there is no record of exploitation in the wild.
  • Probability of exploitation in the next 30 days: 96.8% (FIRST EPSS); higher than 99.8% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: httpd (AlmaLinux:8) 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma; httpd-devel (AlmaLinux:8) 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma; httpd-filesystem (AlmaLinux:8) 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma.
  • Mentioned 6 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Don’t wait for the next maintenance window. Upgrade to httpd (AlmaLinux:8) 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma; httpd-devel (AlmaLinux:8) 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma; httpd-filesystem (AlmaLinux:8) 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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
Dec 20, 2021
Updated
Jun 17, 2026
EPSS
96.8% · 99th percentile

Report tools

JSON

Action score

68

This week

Don’t wait for the next maintenance window.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
29 / 30 · 96.8%

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  • Not in KEV: no record of exploitation in the wild
  • Proof of concept exists, no weaponized module
  • A fix has been released

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
apachehttp server
fedoraprojectfedora
debiandebian linux
tenabletenable.sc
netappcloud backup
oraclecommunications element manager
oraclecommunications operations monitor
oraclecommunications session report manager
oraclecommunications session route manager
oraclehttp server
oracleinstantis enterprisetrack
oraclezfs storage appliance kit

and 2 more

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When you'll hear from us

  • when a new CVE affecting this product is published
  • when a record in your stack enters KEV or is weaponized

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits every 10 minutes on paid plans, on the hour on the free plan.

Is Apache HTTP Server on your server exposed to the internet?Run a port scan

Your free account also gets you

  • CVE alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools, at most 30 a day (3 a day without an account), an API key and MCP
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Versions reported by the vendor

Affected version ranges reported by the assigning authority (apache). Independent of NVD's CPE analysis and usually ahead of it.

  • Apache Software Foundation Apache HTTP Server

    • Apache HTTP Server 2.4 and later · up to and including 2.4.51affected

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • apache http serverbefore 2.4.52

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8httpdbefore 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma
AlmaLinux:8httpd-develbefore 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma
AlmaLinux:8httpd-filesystembefore 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma
AlmaLinux:8httpd-manualbefore 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma
AlmaLinux:8httpd-toolsbefore 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma
AlmaLinux:8mod_http2before 1.15.7-3.module_el8.5.0+2609+b30d9eec1.15.7-3.module_el8.5.0+2609+b30d9eec
AlmaLinux:8mod_ldapbefore 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma
AlmaLinux:8mod_mdbefore 1:2.0.8-8.module_el8.5.0+2609+b30d9eec1:2.0.8-8.module_el8.5.0+2609+b30d9eec
AlmaLinux:8mod_mdbefore 1:2.0.8-8.module_el8.6.0+2872+fe0ff7aa1:2.0.8-8.module_el8.6.0+2872+fe0ff7aa
AlmaLinux:8mod_proxy_htmlbefore 1:2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma1:2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma
AlmaLinux:8mod_sessionbefore 2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma
AlmaLinux:8mod_sslbefore 1:2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma1:2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma
Alpine:v3.12apache2before 2.4.52-r02.4.52-r0
Debian:10apache2before 2.4.38-3+deb10u72.4.38-3+deb10u7
Debian:11apache2before 2.4.52-1~deb11u22.4.52-1~deb11u2
Debian:12apache2before 2.4.52-12.4.52-1
Debian:9apache2before 2.4.25-3+deb9u122.4.25-3+deb9u12
openSUSE:Leap 15.3apache2before 2.4.51-3.37.12.4.51-3.37.1
openSUSE:Leap 15.3chromiumbefore 99.0.4844.84-bp153.2.75.199.0.4844.84-bp153.2.75.1
openSUSE:Tumbleweedapache2before 2.4.52-1.12.4.52-1.1
Red Hat:enterprise_linux:7::clienthttpdbefore 0:2.4.6-97.el7_9.40:2.4.6-97.el7_9.4
Red Hat:enterprise_linux:7::clienthttpd-debuginfobefore 0:2.4.6-97.el7_9.40:2.4.6-97.el7_9.4
Red Hat:enterprise_linux:7::clienthttpd-develbefore 0:2.4.6-97.el7_9.40:2.4.6-97.el7_9.4
Red Hat:enterprise_linux:7::clienthttpd-manualbefore 0:2.4.6-97.el7_9.40:2.4.6-97.el7_9.4

+96

Same product

apache: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-42013Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773)KEV
    99Now
  • CVE-2021-41773Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49KEV
    99Now
  • CVE-2024-38475Apache HTTP Server weakness in mod_rewrite when first segment of substitution matches filesystem path.KEV
    96Now

Published before and after this one in the same product

  • ← EarlierCVE-2021-41524Oct 5, 2021 · null pointer dereference in h2 fuzzing
    38Monitor
  • ← EarlierCVE-2021-44224Dec 20, 2021 · Possible NULL dereference or SSRF in forward proxy configurations in Apache HTTP Server 2.4.51 and earlier
    57Plan
  • Later →CVE-2022-22719Mar 14, 2022 · mod_lua Use of uninitialized value of in r:parsebody
    51Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:httpd2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma · AlmaLinux:8Package registry (OSV)
almalinux:httpd-devel2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma · AlmaLinux:8Package registry (OSV)
almalinux:httpd-filesystem2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma · AlmaLinux:8Package registry (OSV)
almalinux:httpd-manual2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma · AlmaLinux:8Package registry (OSV)
almalinux:httpd-tools2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma · AlmaLinux:8Package registry (OSV)
almalinux:mod_http21.15.7-3.module_el8.5.0+2609+b30d9eec · AlmaLinux:8Package registry (OSV)
almalinux:mod_ldap2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma · AlmaLinux:8Package registry (OSV)
almalinux:mod_md1:2.0.8-8.module_el8.5.0+2609+b30d9eec · AlmaLinux:8Package registry (OSV)
almalinux:mod_proxy_html1:2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma · AlmaLinux:8Package registry (OSV)
almalinux:mod_session2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma · AlmaLinux:8Package registry (OSV)
almalinux:mod_ssl1:2.4.37-43.module_el8.5.0+2609+b30d9eec.1.alma · AlmaLinux:8Package registry (OSV)
alpine:apache22.4.52-r0 · Alpine:v3.12Package registry (OSV)
debian:apache22.4.52-1 · Debian:12Package registry (OSV)
opensuse:apache22.4.51-3.37.1 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:chromium99.0.4844.84-bp153.2.75.1 · openSUSE:Leap 15.3Package registry (OSV)
red hat:httpd0:2.4.6-97.el7_9.4 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:httpd-debuginfo0:2.4.6-97.el7_9.4 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:httpd-debugsource0:2.4.37-21.module+el8.2.0+13808+dea277df.3 · Red Hat:rhel_eus:8.2::appstreamPackage registry (OSV)
red hat:httpd-devel0:2.4.6-97.el7_9.4 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:httpd-filesystem0:2.4.37-21.module+el8.2.0+13808+dea277df.3 · Red Hat:rhel_eus:8.2::appstreamPackage registry (OSV)
red hat:httpd-manual0:2.4.6-97.el7_9.4 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:httpd-tools0:2.4.6-97.el7_9.4 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:httpd-tools-debuginfo0:2.4.37-21.module+el8.2.0+13808+dea277df.3 · Red Hat:rhel_eus:8.2::appstreamPackage registry (OSV)
red hat:mod_ldap0:2.4.6-97.el7_9.4 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:mod_proxy_html1:2.4.6-97.el7_9.4 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:mod_session0:2.4.6-97.el7_9.4 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:mod_ssl1:2.4.6-97.el7_9.4 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
rocky linux:httpd0:2.4.37-39.module+el8.4.0+571+fd70afb1 · Rocky Linux:8Package registry (OSV)
rocky linux:mod_http20:1.15.7-3.module+el8.4.0+553+7a69454b · Rocky Linux:8Package registry (OSV)
rocky linux:mod_md1:2.0.8-8.module+el8.5.0+695+1fa8055e · Rocky Linux:8Package registry (OSV)

+2

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Exploit-DB entry ×1
  • Proof-of-concept repository on GitHub ×3

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHub3 repositories2023-12-05 → 2026-09-19
Exploit-DB entrywebapps2023-04-01

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. First PoC+467 d
  3. TodayNov 14, 2026+1790 d

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Not on record for this CVE: EPSS history · patch commit or PR link · variant or chain candidate.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-787 · Out-of-bounds Write

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

References

Show all references (18 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records