Vulnerability record

CVE-2023-44487

HTTP/2 Rapid Reset Attack Vulnerability

HighExploitation confirmedCISA KEV

What should I do?

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog: attackers are using it. If you run HTTP/2, fix it now.

CISA 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.

US federal civilian agencies must remediate by Oct 31, 2023.

Patch status

Official fix available since Sep 30, 2026

Apply the vendor's update to every affected system. Check the fixed-in versions below where known.

Basis: NVD patch reference

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.

Source: NIST National Vulnerability Database. Official vulnerability data, reproduced as published.

Affected products

Products affected by this vulnerability, with versions and the source of each entry
Product	Vendor	Affected versions	Fixed in	Source
Apache Tomcat	Apache Software Foundation	>= 8.5.0, <= 8.5.93; >= 9.0.0, <= 9.0.80; >= 10.1.0, <= 10.1.13; 11.0.0	—	NVD
APISIX	Apache Software Foundation	< 3.6.1	3.6.1	NVD
Cisco networking & security	Cisco	< 17.15.1	17.15.1	NVD
HTTP/2	IETF	—	—	KEV
IOS XR	Cisco	< 7.11.2	7.11.2	NVD
Jenkins	Jenkins	<= 2.414.2; <= 2.427	—	NVD
NGINX	F5	>= 1.9.5, <= 1.25.2	—	NVD
NX-OS	Cisco	< 10.2\(7\); >= 10.3\(1\), < 10.3\(5\); >= 10.4\(1\), < 10.4\(2\)	10.2\(7\); 10.3\(5\); 10.4\(2\)	NVD
Solr	Apache Software Foundation	< 9.4.0	9.4.0	NVD

Sources: NVD = NIST National Vulnerability Database; KEV = CISA Known Exploited Vulnerabilities catalog.

Intelligence timeline

Developments from the last 30 days, newest first.

CVSS scoredUpdateKEVSep 30, 2026
CVE-2023-44487 scored CVSS 7.5: IETF HTTP/2, HTTP/2 Rapid Reset Attack Vulnerability
CISA lists this as exploited in the wild. Unpatched HTTP/2 systems are exposed to active attacks now.
Basis: NIST National Vulnerability Database
Patch releasedUpdateKEVSep 30, 2026
Patch released for CVE-2023-44487: IETF HTTP/2, HTTP/2 Rapid Reset Attack Vulnerability
An official fix is now available for IETF HTTP/2. This vulnerability is being exploited, so apply it promptly.
Basis: NVD patch reference

1 earlier event is available with a subscription. See plans.

Coverage

We have not published a story about this vulnerability yet.

References

cisa.gov https://www.cisa.gov/news-events/alerts/2023/10/10/http2-rapid-reset-vulnerability-cve-2023-44487
blog.cloudflare.com https://blog.cloudflare.com/technical-breakdown-http2-rapid-reset-ddos-attack/
nvd.nist.gov https://nvd.nist.gov/vuln/detail/CVE-2023-44487
openwall.com http://www.openwall.com/lists/oss-security/2023/10/10/6
openwall.com http://www.openwall.com/lists/oss-security/2023/10/10/7
openwall.com http://www.openwall.com/lists/oss-security/2023/10/13/4
openwall.com http://www.openwall.com/lists/oss-security/2023/10/13/9
openwall.com http://www.openwall.com/lists/oss-security/2023/10/18/4
openwall.com http://www.openwall.com/lists/oss-security/2023/10/18/8
openwall.com http://www.openwall.com/lists/oss-security/2023/10/19/6
openwall.com http://www.openwall.com/lists/oss-security/2023/10/20/8
access.redhat.com https://access.redhat.com/security/cve/cve-2023-44487
arstechnica.com https://arstechnica.com/security/2023/10/how-ddosers-used-the-http-2-protocol-to-deliver-attacks-of-unpreceden…
aws.amazon.com https://aws.amazon.com/security/security-bulletins/AWS-2023-011/
blog.cloudflare.com https://blog.cloudflare.com/zero-day-rapid-reset-http2-record-breaking-ddos-attack/
blog.litespeedtech.com https://blog.litespeedtech.com/2023/10/11/rapid-reset-http-2-vulnerablilty/
blog.qualys.com https://blog.qualys.com/vulnerabilities-threat-research/2023/10/10/cve-2023-44487-http-2-rapid-reset-attack
blog.vespa.ai https://blog.vespa.ai/cve-2023-44487/
bugzilla.proxmox.com https://bugzilla.proxmox.com/show_bug.cgi?id=4988
bugzilla.redhat.com https://bugzilla.redhat.com/show_bug.cgi?id=2242803
bugzilla.suse.com https://bugzilla.suse.com/show_bug.cgi?id=1216123
cgit.freebsd.org https://cgit.freebsd.org/ports/commit/?id=c64c329c2c1752f46b73e3e6ce9f4329be6629f9
cloud.google.com https://cloud.google.com/blog/products/identity-security/google-cloud-mitigated-largest-ddos-attack-peaking-ab…
cloud.google.com https://cloud.google.com/blog/products/identity-security/how-it-works-the-novel-http2-rapid-reset-ddos-attack
community.traefik.io https://community.traefik.io/t/is-traefik-vulnerable-to-cve-2023-44487/20125
discuss.hashicorp.com https://discuss.hashicorp.com/t/hcsec-2023-32-vault-consul-and-boundary-affected-by-http-2-rapid-reset-denial-…
edg.io https://edg.io/lp/blog/resets-leaks-ddos-and-the-tale-of-a-hidden-cve
forums.swift.org https://forums.swift.org/t/swift-nio-http2-security-update-cve-2023-44487-http-2-dos/67764
gist.github.com https://gist.github.com/adulau/7c2bfb8e9cdbe4b35a5e131c66a0c088
github.com https://github.com/Azure/AKS/issues/3947