CVE-2021-31618
This led to a NULL pointer dereference on initialised memory, crashing reliably the child process.
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 51.5%, higher than 99% of all known CVEs. Patch or mitigate before the next change window.
Description
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.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 51.49% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-476
- Affected
- apache/http server · fedoraproject/fedora · debian/debian linux · oracle/enterprise manager ops center · oracle/instantis enterprisetrack · oracle/zfs storage appliance kit
- Source
- security@apache.org
EPSS 51.5% since 3 November 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- http://httpd.apache.org/security/vulnerabilities_24.htmlRelease Notes, Vendor Advisory
- http://www.openwall.com/lists/oss-security/2021/06/10/9Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2024/03/13/2
- https://lists.apache.org/thread.html/r14b66ef0f4f569fd515a3f96cd4eb58bd9a8ff525cc326bb0359664f%40%3Ccvs.httpd.apache.org%3E
- https://lists.apache.org/thread.html/r783b6558abf3305b17ea462bed4bd66d82866438999bf38cef6d11d1%40%3Ccvs.httpd.apache.org%3E
- https://lists.debian.org/debian-lts-announce/2021/07/msg00006.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2NKJ3ZA3FTSZ2QBBPKS6BYGAWYRABNQQ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/A73QJ4HPUMU26I6EULG6SCK67TUEXZYR/
- https://seclists.org/oss-sec/2021/q2/206Mailing List, Third Party Advisory
- https://security.gentoo.org/glsa/202107-38Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210727-0008/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4937Third Party Advisory
- https://www.oracle.com/security-alerts/cpuoct2021.htmlPatch, Third Party Advisory
- http://httpd.apache.org/security/vulnerabilities_24.htmlRelease Notes, Vendor Advisory
- http://www.openwall.com/lists/oss-security/2021/06/10/9Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2024/03/13/2
- https://lists.apache.org/thread.html/r14b66ef0f4f569fd515a3f96cd4eb58bd9a8ff525cc326bb0359664f%40%3Ccvs.httpd.apache.org%3E
- https://lists.apache.org/thread.html/r783b6558abf3305b17ea462bed4bd66d82866438999bf38cef6d11d1%40%3Ccvs.httpd.apache.org%3E
- https://lists.debian.org/debian-lts-announce/2021/07/msg00006.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2NKJ3ZA3FTSZ2QBBPKS6BYGAWYRABNQQ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/A73QJ4HPUMU26I6EULG6SCK67TUEXZYR/
- https://seclists.org/oss-sec/2021/q2/206Mailing List, Third Party Advisory
- https://security.gentoo.org/glsa/202107-38Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210727-0008/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4937Third Party Advisory
- https://www.oracle.com/security-alerts/cpuoct2021.htmlPatch, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.