Security Resilience

CVE-2023-44487

DoS in Apache Tomcat 8.5.0 – 8.5.93

CISA KEVActive ExploitationEUVD ExploitedPublic PoCDoS
Published
10 October 2023
Modified
11 August 2026
KEV Added
10 October 2023
Patch / advisory
CVSS Score v3.1 7.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.99 100.0th percentile
Risk Priority 84 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2023-44487 is a high-severity Uncontrolled Resource Consumption (CWE-400) vulnerability in Apache Tomcat. Its CVSS base score is 7.5 (High).

Operationally, ranked in the top 0.0% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

The vulnerability CVE-2023-44487 is a denial-of-service flaw in the HTTP/2 protocol that stems from rapid request cancellation, which allows an attacker to reset many streams in quick succession and exhaust server resources. It affects any HTTP/2 server implementation that processes such cancellations without sufficient rate limiting or resource controls, and carries a CVSS 3.1 score of 7.5 reflecting high availability impact over a network with no authentication required.

Unauthenticated remote attackers can exploit the issue by sending a flood of HTTP/2 requests followed by immediate RST_STREAM frames, driving up CPU and memory consumption on the target server until it becomes unresponsive. The flaw was actively exploited in the wild between August and October 2023.

Multiple oss-security advisories referenced in the disclosure discuss vendor-specific patches and configuration changes to mitigate stream-reset abuse. The EPSS score has remained near its peak of 0.9450 with a current value of 0.9439, indicating sustained exploitation interest following public release.

EU & UK References

Vulnerability Data

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.

CWE(s)
KEV Date Added
10 October 2023

Related Threats

Threat-Actor AttributionAI

Apple Inc. (Masimo pulse-oximetry trade-secret 2020-2024)
2023 Top Routinely Exploited Vulnerabilities | CISA
Microsoft Corp. (Salesforce / Slack engineer recruitment claims)
2023 Top Routinely Exploited Vulnerabilities | CISA
AnonOps
2023 Top Routinely Exploited Vulnerabilities | CISA
Clop
2023 Top Routinely Exploited Vulnerabilities | CISA

CVEs Like This One

CVE-2021-44228Same product: Cisco Business Process Automationboth on KEV
CVE-2021-40438Same product: Debian Debian Linuxboth on KEV
CVE-2023-4911Same product: Debian Debian Linuxboth on KEV
CVE-2019-0211Same product: Debian Debian Linuxboth on KEV
CVE-2017-12617Same product: Apache Tomcatboth on KEV
CVE-2023-50868Same product: Debian Debian Linux
CVE-2023-41993Same product: Debian Debian Linuxboth on KEV
CVE-2016-8735Same product: Apache Tomcatboth on KEV
CVE-2019-13272Same product: Debian Debian Linuxboth on KEV
CVE-2022-0492Same product: Debian Debian Linuxboth on KEV

Affected Assets

siemens
simatic s7-1500 cpu 1518f-4 pn\/dp mfp firmware
≥ 3.1.5
siemens
sinec ins
1.0 · ≤ 1.0
siemens
sinec nms
≤ 3.0
siemens
st7 scadaconnect
≤ 1.1
siemens
ruggedcom ape1808 firmware
all versions
siemens
simatic s7-1500 cpu 1518-4 pn\/dp mfp firmware
≥ 3.1.5
siemens
siplus s7-1500 cpu 1518-4 pn\/dp mfp firmware
≥ 3.1.5
ietf
http
2.0
nghttp2
nghttp2
≤ 1.57.0
netty
netty
≤ 4.1.100
+155 more product configuration(s) — see NVD for full list

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-400

Limiting concurrent sessions directly prevents uncontrolled resource consumption by capping the number of active sessions per user or account.

addresses: CWE-400

Analysis identifies uncontrolled resource consumption indicative of denial-of-service or abuse attempts.

addresses: CWE-400

Contingency plan testing includes resource exhaustion scenarios to verify recovery, making it harder for attackers to sustain exploits that cause uncontrolled consumption.

addresses: CWE-400

Updated contingency plans include current procedures to detect, contain, and recover from resource exhaustion, limiting an attacker's ability to sustain impact from uncontrolled consumption.

addresses: CWE-400

Alternate site allows resumption of operations if resource exhaustion at the primary site is exploited to cause unavailability.

addresses: CWE-400

Alternate telecommunications services enable resumption of essential functions when primary services become unavailable due to uncontrolled resource consumption.

addresses: CWE-400

The team can analyze and respond to resource exhaustion incidents, reducing the impact of attacks that exploit uncontrolled consumption weaknesses.

addresses: CWE-400

Timely maintenance support and spare parts enable rapid recovery from failures induced by uncontrolled resource consumption, shortening the impact window of denial-of-service attacks.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

finds

Pre-agreed severity-based prioritization and resource allocation during incident triage reduce the likelihood that an attacker-induced resource exhaustion will overwhelm the organization before corrective action is taken.

finds

Early notification of anomalous resource consumption or system malfunctions enables throttling or isolation before availability is lost.

A.8.15 Logging partial match
finds

Specifying log storage limits and rotation procedures reduces the risk that unbounded log growth will exhaust disk or memory resources and cause denial of service.

finds

Resource-utilization monitoring and alerting on bottlenecks or overloads limits the impact of denial-of-service or resource-exhaustion attacks.

blocks

A.8.20 implements network-level protections (firewalls, segmentation, protocol hardening, monitoring, authentication of systems/devices) that can limit abuse of a resource-consuming weakness but do not stop the weakness from being exploitable; the flaw remains present in the product and can still be triggered from an authorized or internal context.

blocks

Monitoring network service usage and applying controls to restrict access when necessary limits an attacker’s ability to consume excessive resources through unrestricted or unauthenticated service calls.

Hardening callouts derived

DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.

  • No fine-grained STIG row for CWE-400, a class-level weakness. Rules are authored against its narrower children: CWE-770.

References