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TI-2021-11716 Aliases CVE-2021-31618GHSA-4jq3-qrx6-87cc

NULL pointer dereference on specially crafted HTTP/2 request

Priority HIGH 71CWE-476Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
No fix listed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-476.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.52142 98th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
ApacheApache HTTP Server2.4.47—No fix listedCNA
  • Apache HTTP Server VendorApache Affected 2.4.47 Fixed in — No fix listed CNA

CPE configurations NVD · 11

CPEVersionsRoleVendor
cpe:2.3:a:apache:http_server:1.15.17:*:*:*:*:*:*:*1.15.17VulnerableApache
cpe:2.3:a:apache:http_server:2.4.47:*:*:*:*:*:*:*2.4.47VulnerableApache
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*33VulnerableFedoraproject
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*34VulnerableFedoraproject
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*9.0VulnerableDebian
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*10.0VulnerableDebian
cpe:2.3:a:oracle:enterprise_manager_ops_center:12.4.0.0:*:*:*:*:*:*:*12.4.0.0VulnerableOracle
cpe:2.3:a:oracle:instantis_enterprisetrack:17.1:*:*:*:*:*:*:*17.1VulnerableOracle
cpe:2.3:a:oracle:instantis_enterprisetrack:17.2:*:*:*:*:*:*:*17.2VulnerableOracle
cpe:2.3:a:oracle:instantis_enterprisetrack:17.3:*:*:*:*:*:*:*17.3VulnerableOracle
  • cpe:2.3:a:apache:http_server:1.15.17:*:*:*:*:*:*:* Versions 1.15.17 Vulnerable ·Apache
  • cpe:2.3:a:apache:http_server:2.4.47:*:*:*:*:*:*:* Versions 2.4.47 Vulnerable ·Apache
  • cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:* Versions 33 Vulnerable ·Fedoraproject
  • cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* Versions 34 Vulnerable ·Fedoraproject
  • cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* Versions 9.0 Vulnerable ·Debian
  • cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* Versions 10.0 Vulnerable ·Debian
  • cpe:2.3:a:oracle:enterprise_manager_ops_center:12.4.0.0:*:*:*:*:*:*:* Versions 12.4.0.0 Vulnerable ·Oracle
  • cpe:2.3:a:oracle:instantis_enterprisetrack:17.1:*:*:*:*:*:*:* Versions 17.1 Vulnerable ·Oracle
  • cpe:2.3:a:oracle:instantis_enterprisetrack:17.2:*:*:*:*:*:*:* Versions 17.2 Vulnerable ·Oracle
  • cpe:2.3:a:oracle:instantis_enterprisetrack:17.3:*:*:*:*:*:*:* Versions 17.3 Vulnerable ·Oracle
Show 1 more CPE
CPEVersionsRoleVendor
cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:*8.8VulnerableOracle
  • cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:* Versions 8.8 Vulnerable ·Oracle

Remediation

No fixed version listed by the sources yet.

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Advisory ·

    Apache HTTP Server — GLSA-202107-38

    7 records Highest priority Priority HIGH 3 HIGH, 4 MEDIUM

    Other records, highest priority first

    • TI-2021-08375 Apache HTTP Server mod_session response handling heap overflowPriority HIGH 79
    • TI-2021-08374 mod_session NULL pointer dereferencePriority HIGH 69
    • TI-2020-17981 mod_auth_digest possible stack overflow by one nul bytePriority MEDIUM 64
    Show all 7 records → Advisory →
  • Advisory ·

    Apache HTTP Server — DSA-4937

    5 records Highest priority Priority HIGH 3 HIGH, 2 MEDIUM

    Other records, highest priority first

    • TI-2021-08375 Apache HTTP Server mod_session response handling heap overflowPriority HIGH 79
    • TI-2021-08374 mod_session NULL pointer dereferencePriority HIGH 69
    • TI-2020-17981 mod_auth_digest possible stack overflow by one nul bytePriority MEDIUM 64
    Show all 5 records → Advisory →

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

Not affected: 8 products
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9
  • Red Hat JBoss Core Services
  • Red Hat JBoss Enterprise Application Platform 6
  • Red Hat JBoss Enterprise Web Server 2
  • Red Hat Software Collections

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-31618
  2. 2026-10-03 Alias added: GHSA-4jq3-qrx6-87cc

References

Patch 1

Advisory 9

Other 3

  • TI-2021-18535 Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) KEVCVSS 3.1CRITICAL 9.8
  • TI-2021-18417 Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49 KEVCVSS 3.1CRITICAL 9.8
  • TI-2024-25716 Apache HTTP Server weakness in mod_rewrite when first segment of substitution matches filesystem path. KEVCVSS 3.1CRITICAL 9.1
  • TI-2021-17490 mod_proxy SSRF KEVCVSS 3.1CRITICAL 9.0
  • TI-2019-00184 Use after free in Apache HTTP Server KEVCVSS 3.1HIGH 7.8
  • TI-2009-03392 The TLS protocol, and the SSL protocol 3.0 and possibly earlier, as used in Microsoft… CVSS 3.1CRITICAL 9.8
See all 349 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences