CVE-2020-13950Network attack vector

Remote service crash via conflicting framing headers

Published Jun 10, 2021 · Updated Aug 4, 2024

NULL pointer dereference in mod_proxy_http in Apache HTTP Server 2.4.41 through 2.4.46 allows remote attackers to crash the server. The module mishandles proxy requests containing both Content-Length and Transfer-Encoding headers and dereferences a null pointer. The request must reach an enabled mod_proxy_http proxy route; exploitation terminates an httpd process and interrupts service without exposing or modifying data.

CVSS severity7.5
High
EPSS probability49.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in mod_proxy_http in Apache HTTP Server 2.4.41 through 2.4.46 allows remote attackers to crash the server. The module mishandles proxy requests containing both Content-Length and Transfer-Encoding headers and dereferences a null pointer. The request must reach an enabled mod_proxy_http proxy route; exploitation terminates an httpd process and interrupts service without exposing or modifying data.

The record

CVE
CVE-2020-13950
Published
Jun 10, 2021
Updated
Aug 4, 2024
Vendor
The Apache Software Foundation
Product
Apache HTTP Server
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.4.41
  2. Affected versionversion=2.4.43
  3. Affected versionversion=2.4.46

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache HTTP Serverversion=2.4.41; version=2.4.43; version=2.4.46

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5Amazon LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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