CVE-2021-31618

NameCVE-2021-31618
DescriptionApache 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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
ReferencesDLA-2706-1, DSA-4937-1
NVD severitymedium
Debian Bugs989562

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
apache2 (PTS)stretch2.4.25-3+deb9u9vulnerable
stretch (security)2.4.25-3+deb9u11fixed
buster2.4.38-3+deb10u5fixed
buster (security)2.4.38-3+deb10u6fixed
bullseye2.4.48-3.1+deb11u1fixed
bullseye (security)2.4.51-1~deb11u1fixed
bookworm, sid2.4.51-2fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
apache2sourceexperimental2.4.48-1
apache2sourcestretch2.4.25-3+deb9u10DLA-2706-1
apache2sourcebuster2.4.38-3+deb10u5DSA-4937-1
apache2source(unstable)2.4.46-5989562

Notes

https://httpd.apache.org/security/vulnerabilities_24.html#CVE-2021-31618
https://github.com/apache/httpd/commit/a4fba223668c554e06bc78d6e3a88f33d4238ae4
https://svn.apache.org/viewvc/httpd/httpd/branches/2.4.x/modules/http2/h2_stream.c?r1=1889759&r2=1889758&pathrev=1889759

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