What is wrong
The HTTP/2 protocol allows excessive server resource consumption when request cancellations reset many streams quickly. An attacker can exploit this vulnerability to cause a denial of service.
Who is affected
This issue affects nginx versions from 1.9.5 through 1.25.2.
What to do
Apply mitigations per vendor instructions or follow applicable cloud guidance. If mitigations are unavailable, discontinue use of the product.
Original description
The HTTP/2 protocol allows a denial of service (server resource consumption) because request cancellation can reset many streams quickly, as exploited in the wild in August through October 2023.
Known exploited (CISA KEV)
- Added to KEV
- 2023-10-10
- Remediation due (US federal)
- 2023-10-31
- Ransomware use
- Unknown
- Required action
- Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Affected software
Details
- Published
- 2023-10-10
- Last modified
- 2026-08-11
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- CWE
- CWE-400
- EPSS (30-day exploit probability)
- 100.00% (percentile 100)
References
- cve.org/CVE-2023-44487
- nvd.nist.gov/vuln/detail/CVE-2023-44487
- www.openwall.com/lists/oss-security/2023/10/10/6
- www.openwall.com/lists/oss-security/2023/10/10/7
- www.openwall.com/lists/oss-security/2023/10/13/4
- www.openwall.com/lists/oss-security/2023/10/13/9
- www.openwall.com/lists/oss-security/2023/10/18/4
- www.openwall.com/lists/oss-security/2023/10/18/8
- www.openwall.com/lists/oss-security/2023/10/19/6
- www.openwall.com/lists/oss-security/2023/10/20/8
- access.redhat.com/security/cve/cve-2023-44487
- arstechnica.com/security/2023/10/how-ddosers-used-the-http-2-protocol-to-deliver-attacks-o...
- aws.amazon.com/security/security-bulletins/AWS-2023-011/
- blog.cloudflare.com/technical-breakdown-http2-rapid-reset-ddos-attack/
Track these versions on your own servers
InfraGuard collects installed software versions from every server and flags the ones with known vulnerabilities. Self-hosted — nothing leaves your network.
This product uses data from the NVD API but is not endorsed or certified by the NVD. CVE® is a registered trademark of The MITRE Corporation; CVE records are used under the CVE Program Terms of Use.