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CVE-2023-44487

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.

Exploited in the wild. In CISA KEV since 2023‑10‑10. A vendor fix is available.

CVSS 3.17.5HighEPSS percentile99th100% chance in 30 daysCISA KEVListedsince 2023-10-10, due 2023-10-31
Public exploit: 2 sourcesFixVendor fixNo build named by the sources

Published Updated Sources: CVE.org, NVD, GitHub, BDU, CSAF

NVD CVE.org

What to do

The vendor has published a fix. Version details are below where the sources state them.

Steps

Written by AI from the record
  1. Check whether you run any of these products in your environment: simatic s7-1500 cpu 1518f-4 pn/dp mfp firmware, simatic s7-1500 cpu 1518-4 pn/dp mfp firmware, siplus s7-1500 cpu 1518-4 pn/dp mfp firmware, sinec ins, sinec nms, st7 scadaconnect, ruggedcom ape1808 firmware, http, nghttp2, netty.
  2. For each affected product, upgrade to the fixed version listed by the vendor (see step 4).
  3. If you cannot upgrade immediately, contact your vendor to confirm available mitigations or temporary defenses for “HTTP/2 rapid reset” style attacks.
  4. Apply the known fixed versions: sinec ins → 1.0; sinec nms → 3.0; st7 scadaconnect → 1.1; nghttp2 → 1.57.0; netty → 4.1.100; jetty → 9.4.53; caddy → 2.7.5; go → 1.20.10; http2 → 0.17.0; networking → 0.17.0; nginx plus → r29; swiftnio http/2 → 1.28.0.
Vendor advisory Usually a quick update
Check it yourselfA free Nuclei and OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Discuss checks for your systems with a specialist. Scope is agreed before testing.

What it is

From the CVE record

Multiple vulnerabilities have been identified in the additional GNU/Linux subsystem of the firmware version V3.1.5 for the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP (incl. SIPLUS variant). Siemens is preparing fix versions and recommends countermeasures for products where fixes are not, or not yet available.

In plain language

Written by AI from the record

CVE-2023-44487 is an HTTP/2 bug that lets attackers overwhelm servers by rapidly cancelling many connection “streams,” and typical small businesses should treat it as urgent to fix if you run affected HTTP/2 software.

CVE-2023-44487 is a denial-of-service weakness in HTTP/2 implementations that allows an attacker to trigger rapid stream resets via request cancellation, consuming server resources; it requires no authentication and has been exploited in the wild (added to CISA KEV on 2023-10-10).

If you're affected

  • Service outage for your applications
  • Web/API performance collapse
  • Business disruption during attacks
  • Higher hosting/network costs

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS99th
Public exploit
CISA KEV
CISA KEV

Listed as exploited in the wild since 2023-10-10.

US federal agencies must remediate by 2023-10-31.

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Public exploits

2 sources with a proof of concept or module.

Exploit links, PoCs and Metasploit modules after sign-in
EPSS

100% chance of exploitation activity in the next 30 days, which ranks it in the 99th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

A public exploit existed 67 days before the patch.

  1. Analysis publishedEPSS vs CVSS vs KEV: which number actually tells you to patch
  2. Patch availableworkaround available, record updated
  3. OpenVAS check added
  4. Patch availableworkaround available, record updated
  5. Public exploit / PoCsource: github-pocnuclei check added
  6. Added to CISA KEVpublished, weakness classified, att&ck mapped

Affected products

And 206 more affected products. See all after sign-in

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Scored 7.5 by NVD.

How it is reached

  • Attack Vector NetworkExploitable remotely over the network without any special conditions
  • Attack Complexity LowNo special conditions — the attack can be reliably reproduced
  • Privileges Required NoneNo authentication required — anyone can exploit this
  • User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

  • Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

  • Confidentiality NoneNo confidentiality impact
  • Integrity NoneNo integrity impact
  • Availability HighTotal denial of service — the component is completely unavailable

Weaknesses

ATT&CK techniques

Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.

Sources

References in the record

And 540 more references. See all after sign-in

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