CVERadar
HIGH · CVSS 3.1 7.5CISA KEV · added 2023-10-10Exploit-DBPublic PoCEPSS 100.00% (p100)Threat level 82

CVE-2023-44487: HTTP/2 Rapid Reset Attack Vulnerability

IETF · HTTP/2 · NVD published 2023-10-10 · posted 2026-10-21 · last modified 2026-08-12

What it is

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.

WeaknessCWE-400
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (source: [email protected])
CISA due date2023-10-31 (for US federal agencies under BOD; a good deadline for everyone)
ATT&CK tacticsInitial Access → Impact

Exploitation evidence

First exploit evidence seen: 2023-10-10 (earliest date across the sources below).

Exploited in the wild

  • CISA KEV: listed since 2023-10-10. Source

Public exploit code

Exploit-DB

  • EDB-52426: HTTP/2 2.0 - Denial Of Service (DOS) (2025-09-16)

GitHub proof-of-concept repositories

26 public repositories from 26 accounts, first seen 2023-10-10. Most starred: bcdannyboy/CVE-2023-44487 (248 stars), view repository.

Verify before running: public PoCs can be malicious. Read the code and only run it in an isolated lab. A PoC means exploit code is public, not that this CVE is exploited in the wild.

Sources: CISA KEV · Exploit-DB (OffSec) · nomi-sec/PoC-in-GitHub.

Defend the Chain

The attack chain for CVE-2023-44487 laid across the MITRE ATT&CK Enterprise tactics. Solid cards come from the MITRE CTID KEV mappings; dashed cards are inferred by CVERadar from the CWE or description. Correct defences are real ATT&CK mitigations for that technique.

Threat level 82/100
Defender level 1 · 0 XP
Chain links broken: 0/2

Reconnaissance

Resource Development

Initial Access

Execution

Persistence

Privilege Escalation

Stealth

Defense Impairment

Credential Access

Discovery

Lateral Movement

Collection

Command and Control

Exfiltration

Impact

Pick a red technique card on the board, then choose the defence that stops it.

Defend against T1190 Exploit Public-Facing Application CTID: exploitation technique

This vulnerability is exploited through a 'Rapid Reset' flaw in HTTP/2 endpoints. Attackers initiate this vulnerability by sending a crafted sequence of HTTP requests using HEADERS followed by RST_STREAM frames. This allows them to generate substantial traffic on targeted servers, significantly increasing CPU usage and leading to resource exhaustion without authentication.

How to fix it

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. (source: CISA KEV)

Fixed versions

  • siemens sinec ins: upgrade to 1.0 or later
  • siemens sinec nms: upgrade to 3.0 or later
  • siemens st7 scadaconnect: upgrade to 1.1 or later
  • nghttp2 nghttp2: upgrade to 1.57.0 or later
  • netty netty: upgrade to 4.1.100 or later
  • eclipse jetty: upgrade to 9.4.53 or later
  • eclipse jetty: upgrade to 10.0.17 or later (affected from 10.0.0)
  • eclipse jetty: upgrade to 11.0.17 or later (affected from 11.0.0)
  • eclipse jetty: upgrade to 12.0.2 or later (affected from 12.0.0)
  • caddyserver caddy: upgrade to 2.7.5 or later
  • golang go: upgrade to 1.20.10 or later
  • golang go: upgrade to 1.21.3 or later (affected from 1.21.0)
  • golang http2: upgrade to 0.17.0 or later
  • golang networking: upgrade to 0.17.0 or later

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

MITRE ATT&CK mitigations for this chain

  • M1048 Application Isolation and Sandboxing (for T1190) : Application isolation will limit what other processes and system features the exploited target can access.
  • M1037 Filter Network Traffic (for T1190, T1499) : Restrict outbound network traffic from public-facing servers to prevent unauthorized connections from initiating communications with attacker-controlled infrastructure. While this may not prevent the initial exploitation, it limits the attacker's ability to verify and control the compromised server post-exploit, reduci
  • M1030 Network Segmentation (for T1190) : Segment externally facing servers and services from the rest of the network with a DMZ or on separate hosting infrastructure.
  • M1016 Vulnerability Scanning (for T1190) : Regularly scan externally facing systems for vulnerabilities and establish procedures to rapidly patch systems when critical vulnerabilities are discovered through scanning and through public disclosure.
  • M1026 Privileged Account Management (for T1190) : Use least privilege for service accounts will limit what permissions the exploited process gets on the rest of the system.
  • M1050 Exploit Protection (for T1190) : Web Application Firewalls may be used to limit exposure of applications to prevent exploit traffic from reaching the application.
  • M1035 Limit Access to Resource Over Network (for T1190) : Ensure that all publicly exposed services are actually intended to be so, and restrict access to any that should only be available internally.
  • M1051 Update Software (for T1190) : Update software regularly by employing patch management for externally exposed applications.

Detection Generic guidance

  • Initial Access: Alert on unusual requests to the affected service (odd paths, oversized payloads, exploit strings) in WAF, reverse-proxy and application logs.
  • Impact: Monitor service availability, unexpected encryption activity and mass file changes.

Response checklist Generic guidance

  1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
  2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
  3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
  4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.

Sources