High 7.5Known exploited (CISA KEV)Published Oct 9, 2023

CVE-2023-44487The 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.

Updated under an hour ago (Oct 26, 2026, 2:50 PM ET)

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It affects ietf http and 57 other products. Add what you run to find out whether that includes you.

CISA lists it as known exploited since Oct 10, 2023; federal agencies had to remediate by Oct 31, 2023. Treat that date as your deadline.

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Exploited in the last 30 days

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: 7.5 HIGH (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-400
Known exploited: Added to CISA KEV Oct 10, 2023; federal remediation due Oct 31, 2023Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
EPSS (exploitation in the next 30 days): 100.00% (percentile 100)
Assigned by: mitre
NVD analysis: Analyzed
Record last updated: Oct 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

ietf http ietf:http	2.0	CISA ADP
Siemens RUGGEDCOM APE1808 siemens:ruggedcom_ape1808 (from the name)	all versions	CISA ADP
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.5	CISA ADP
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name)	from V3.1.5	CISA ADP
Siemens SINEC NMS siemens:sinec_nms (from the name)	before V3.0	CISA ADP
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.5	CISA ADP
siemens simatic_s7-1500_cpu_1518f-4_pn/dp_mfp_firmware siemens:simatic_s7-1500_cpu_1518f-4_pn/dp_mfp_firmware	from 3.1.5	NVD
siemens sinec_ins siemens:sinec_ins	before 1.0; 1.0; 1.0; 1.0; 1.0; 1.0	NVD
siemens sinec_nms siemens:sinec_nms	before 3.0	NVD
siemens st7_scadaconnect siemens:st7_scadaconnect	before 1.1	NVD
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References

References

https://github.com/dotnet/core/blob/e4613450ea0da7fd2fc6b61dfb2c1c1dec1ce9ec/release-notes/6.0/6.0.23/6.0.23.md?plain=1#L73
https://blog.cloudflare.com/technical-breakdown-http2-rapid-reset-ddos-attack/	technical-description, vendor-advisory
https://aws.amazon.com/security/security-bulletins/AWS-2023-011/	third-party-advisory
https://cloud.google.com/blog/products/identity-security/how-it-works-the-novel-http2-rapid-reset-ddos-attack	technical-description, vendor-advisory
https://www.nginx.com/blog/http-2-rapid-reset-attack-impacting-f5-nginx-products/
https://cloud.google.com/blog/products/identity-security/google-cloud-mitigated-largest-ddos-attack-peaking-above-398-million-rps/	technical-description, vendor-advisory
https://news.ycombinator.com/item?id=37831062
https://blog.cloudflare.com/zero-day-rapid-reset-http2-record-breaking-ddos-attack/	third-party-advisory, vendor-advisory
https://www.phoronix.com/news/HTTP2-Rapid-Reset-Attack
https://github.com/envoyproxy/envoy/pull/30055
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The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.