NULL pointer dereference in Apache HTTP Server
CVE-2021-31618
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 · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.515 (98.9th percentile), scored .
High probability of exploitation in the next 30 days — patch promptly. 99th percentile — 98.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.515 · newest: 0.515 · change: 0.000
Affected products
- Apache HTTP Server — versions 1.15.17, 2.4.47
- Apache Software Foundation HTTP Server — versions 2.4.47
- Oracle Enterprise Manager Ops Center — versions 12.4.0.0
- Oracle Instantis Enterprisetrack — versions 17.1, 17.2, 17.3
- Oracle Zfs Storage Appliance Kit — versions 8.8
- Debian Linux — versions 9.0, 10.0
- Fedoraproject Fedora — versions 33, 34
Weakness classification (CWE)
Public proof-of-concept exploits
References
- httpd.apache.org/security/vulnerabilities_24.html (Release Notes, Vendor Advisory)
- www.openwall.com/lists/oss-security/2021/06/10/9 (mailing-list, Mailing List, Third Party Advisory)
- seclists.org/oss-sec/2021/q2/206 (Mailing List, Third Party Advisory)
- lists.apache.org/thread.html/r14b66ef0f4f569fd515a3f96cd4eb58bd9a8ff525cc326bb0… (mailing-list)
- lists.apache.org/thread.html/r783b6558abf3305b17ea462bed4bd66d82866438999bf38ce… (mailing-list)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
- lists.debian.org/debian-lts-announce/2021/07/msg00006.html (mailing-list, Mailing List, Third Party Advisory)
- www.debian.org/security/2021/dsa-4937 (vendor-advisory, Third Party Advisory)
- security.gentoo.org/glsa/202107-38 (vendor-advisory, Third Party Advisory)
Frequently asked questions
- What is CVE-2021-31618?
- CVE-2021-31618 is a high-severity vulnerability in Apache HTTP Server, classified under NULL Pointer Dereference. CVSS score: 7.5/10. Published 2021-06-15.
- How severe is CVE-2021-31618?
- High severity. CVSS v3 base score is 7.5 out of 10.
- Is CVE-2021-31618 known to be exploited?
- 8 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.