CVE-2021-34798Network attack vector

Server-process crash via malformed request dereference

Published Sep 16, 2021 · Updated Aug 4, 2024

NULL pointer dereference in Apache HTTP Server 2.4.48 and earlier allows remote attackers to crash server processing via malformed requests. The Apache advisory identifies the locus only as the httpd core and does not disclose which request field reaches the invalid dereference. No authentication or user interaction is required; the documented consequence is limited to availability loss from a server-process crash.

CVSS severity7.5
High
EPSS probability64.51%
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 Apache HTTP Server 2.4.48 and earlier allows remote attackers to crash server processing via malformed requests. The Apache advisory identifies the locus only as the httpd core and does not disclose which request field reaches the invalid dereference. No authentication or user interaction is required; the documented consequence is limited to availability loss from a server-process crash.

The record

CVE
CVE-2021-34798
Published
Sep 16, 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. Sep 16, 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=Apache HTTP Server 2.4 <=2.4.48

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache HTTP Serverversion=Apache HTTP Server 2.4 <=2.4.48

Published CVSS scores

7.5NIST National Vulnerability DatabaseCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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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