Apache HTTP Server protocol handler for the HTTP/2 protocol checks received request headers against the size limitations as configured for the server and used for the HTTP/1 protocol as well. On violation of these restrictions and HTTP response is sent to the client with a status code indicating why the request was rejected. This rejection response was not fully initialised in the HTTP/2 protocol handler if the offending header was the very first one received or appeared in a a footer. This led to a NULL pointer dereference on initialised memory, crashing reliably the child process. Since such a triggering HTTP/2 request is easy to craft and submit, this can be exploited to DoS the server. This issue affected mod_http2 1.15.17 and Apache HTTP Server version 2.4.47 only. Apache HTTP Server 2.4.47 was never released.
Published 2021-06-15 09:15:08
Updated 2021-12-10 17:05:25
View at NVD,   CVE.org
Vulnerability category: Memory CorruptionDenial of service

Threat overview for CVE-2021-31618

Top countries where our scanners detected CVE-2021-31618
Top open port discovered on systems with this issue 80
IPs affected by CVE-2021-31618 8,780
Threat actors abusing to this issue? Yes
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Exploit prediction scoring system (EPSS) score for CVE-2021-31618

Probability of exploitation activity in the next 30 days: 1.75%

Percentile, the proportion of vulnerabilities that are scored at or less: ~ 88 % EPSS Score History EPSS FAQ

CVSS scores for CVE-2021-31618

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source
5.0
MEDIUM AV:N/AC:L/Au:N/C:N/I:N/A:P
10.0
2.9
NIST
7.5
HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.9
3.6
NIST

CWE ids for CVE-2021-31618

  • A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.
    Assigned by:
    • nvd@nist.gov (Primary)
    • security@apache.org (Secondary)

References for CVE-2021-31618

Products affected by CVE-2021-31618

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