CVE-2023-44487Known exploitationPublic exploitNetwork attack vector

Service interruption via rapid stream cancellation

Published Oct 10, 2023 · Updated Jul 14, 2026

Resource exhaustion in HTTP/2 implementations allows remote attackers to interrupt service with rapid stream cancellations. A client opens many request streams, sends each request, and immediately issues RST_STREAM, leaving the server to process costly work while the connection remains open. An unauthenticated network path to an HTTP/2 endpoint is sufficient, and sustained requests can exhaust server resources and deny service.

CVSS severity7.5
High
EPSS probability100.00%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in HTTP/2 implementations allows remote attackers to interrupt service with rapid stream cancellations. A client opens many request streams, sends each request, and immediately issues RST_STREAM, leaving the server to process costly work while the connection remains open. An unauthenticated network path to an HTTP/2 endpoint is sufficient, and sustained requests can exhaust server resources and deny service.

The record

CVE
CVE-2023-44487
Published
Oct 10, 2023
Updated
Jul 14, 2026
Vendor
Siemens
Product
SINEC NMS
Classifications
CWE-400, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 1, 2023Exploitation reportedGoogle-observed Rapid Reset DDoS campaign
  2. Oct 10, 2023CVE publishedPublication date reported by the CVE source.
  3. Oct 10, 2023Exploitation reportedCISA Known Exploited Vulnerabilities catalog entry
  4. Jul 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <V3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Siemens · SINEC NMSversion=0 <V3.0
Siemens · SIPLUS S7-1500 CPU 1518-4 PN/DP MFPversion=V3.1.5 <*
Siemens · RUGGEDCOM APE1808version=0 <*
Siemens · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPversion=V3.1.5 <*
Siemens · SIMATIC S7-1500 CPU 1518-4 PN/DP MFPversion=V3.1.5 <*
Internet Engineering Task Force (IETF) · Hypertext Transfer Protocol (HTTP)version=2.0

Published CVSS scores

8.7Siemens ProductCERTCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5Siemens ProductCERTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.002Endpoint Denial of Service: Service Exhaustion Flood

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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