CVE-2023-44487
HTTP/2 Rapid Reset Attack Vulnerability
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 31 October 2023). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
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.
- 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
- 100.00% probability · 100th percentile
- Public exploits
- 1 in Exploit-DB · first 16 September 2025
- CISA KEV
- Listed 10 October 2023 · due 31 October 2023
- Weakness
- CWE-400
- Affected
- siemens/simatic s7-1500 cpu 1518f-4 pn\/dp mfp firmware · siemens/sinec ins · siemens/sinec nms · siemens/st7 scadaconnect · siemens/ruggedcom ape1808 firmware · siemens/simatic s7-1500 cpu 1518-4 pn\/dp mfp firmware · siemens/siplus s7-1500 cpu 1518-4 pn\/dp mfp firmware · ietf/http · nghttp2/nghttp2 · netty/netty · envoyproxy/envoy · eclipse/jetty · caddyserver/caddy · golang/go · golang/http2 · golang/networking · f5/big-ip access policy manager · f5/big-ip advanced firewall manager · f5/big-ip advanced web application firewall · f5/big-ip analytics · +40 more
- Source
- cve@mitre.org
EPSS 100.0% since 30 October 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.
CISA notes
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. This vulnerability affects a common open-source component, third-party library, or protocol used by different products. For more information, please see: HTTP/2 Rapid Reset Vulnerability, CVE-2023-44487 | CISA: https://www.cisa.gov/news-events/alerts/2023/10/10/http2-rapid-reset-vulnerability-cve-2023-44487; https://blog.cloudflare.com/technical-breakdown-http2-rapid-reset-ddos-attack/; https://nvd.nist.gov/vuln/detail/CVE-2023-44487
Public exploits (1)
Entries in Exploit-DB that cite this CVE. Links go to the Exploit-DB page and to the file in the public repository; nothing is hosted here. A verified tick means the Exploit-DB team confirmed the exploit works against the stated version.
References
- http://www.openwall.com/lists/oss-security/2023/10/10/6Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2023/10/10/7Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2023/10/13/4Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2023/10/13/9Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2023/10/18/4Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2023/10/18/8Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2023/10/19/6Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2023/10/20/8Mailing List, Third Party Advisory
- https://access.redhat.com/security/cve/cve-2023-44487Vendor Advisory
- https://arstechnica.com/security/2023/10/how-ddosers-used-the-http-2-protocol-to-deliver-attacks-of-unprecedented-size/Press/Media Coverage, Third Party Advisory
- https://aws.amazon.com/security/security-bulletins/AWS-2023-011/Third Party Advisory
- https://blog.cloudflare.com/technical-breakdown-http2-rapid-reset-ddos-attack/Technical Description, Vendor Advisory
- https://blog.cloudflare.com/zero-day-rapid-reset-http2-record-breaking-ddos-attack/Third Party Advisory, Vendor Advisory
- https://blog.litespeedtech.com/2023/10/11/rapid-reset-http-2-vulnerablilty/Vendor Advisory
- https://blog.qualys.com/vulnerabilities-threat-research/2023/10/10/cve-2023-44487-http-2-rapid-reset-attackPress/Media Coverage, Third Party Advisory
- https://blog.vespa.ai/cve-2023-44487/Vendor Advisory
- https://bugzilla.proxmox.com/show_bug.cgi?id=4988Issue Tracking, Third Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2242803Issue Tracking, Vendor Advisory
- https://bugzilla.suse.com/show_bug.cgi?id=1216123Issue Tracking, Vendor Advisory
- https://cgit.freebsd.org/ports/commit/?id=c64c329c2c1752f46b73e3e6ce9f4329be6629f9Mailing List, Patch, Vendor Advisory
- https://cloud.google.com/blog/products/identity-security/google-cloud-mitigated-largest-ddos-attack-peaking-above-398-million-rps/Technical Description, Vendor Advisory
- https://cloud.google.com/blog/products/identity-security/how-it-works-the-novel-http2-rapid-reset-ddos-attackTechnical Description, Vendor Advisory
- https://community.traefik.io/t/is-traefik-vulnerable-to-cve-2023-44487/20125Vendor Advisory
- https://discuss.hashicorp.com/t/hcsec-2023-32-vault-consul-and-boundary-affected-by-http-2-rapid-reset-denial-of-service-vulnerability-cve-2023-44487/59715Third Party Advisory
- https://edg.io/lp/blog/resets-leaks-ddos-and-the-tale-of-a-hidden-cveBroken Link
- https://forums.swift.org/t/swift-nio-http2-security-update-cve-2023-44487-http-2-dos/67764Vendor Advisory
- https://gist.github.com/adulau/7c2bfb8e9cdbe4b35a5e131c66a0c088Issue Tracking, Patch
- https://github.com/Azure/AKS/issues/3947Issue Tracking
- https://github.com/Kong/kong/discussions/11741Issue Tracking
- https://github.com/advisories/GHSA-qppj-fm5r-hxr3Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.