CVE-2021-1312Network attack vector

Health monitor API outage via TCP backlog exhaustion

Published Jan 20, 2021 · Updated Nov 12, 2024

Resource exhaustion in Cisco Elastic Services Controller 5.3.0.94 and earlier allows remote attackers to interrupt the health monitor API. Undersized kernel limits for maximum TCP connections and the SYN backlog let a crafted TCP packet flood occupy the API's listening ports. The issue is remotely reachable without authentication only when the health monitor API is in use, and the bounded result is loss of that API rather than data access or modification.

CVSS severity5.3
Medium
EPSS probability2.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Cisco Elastic Services Controller 5.3.0.94 and earlier allows remote attackers to interrupt the health monitor API. Undersized kernel limits for maximum TCP connections and the SYN backlog let a crafted TCP packet flood occupy the API's listening ports. The issue is remotely reachable without authentication only when the health monitor API is in use, and the bounded result is loss of that API rather than data access or modification.

The record

CVE
CVE-2021-1312
Published
Jan 20, 2021
Updated
Nov 12, 2024
Vendor
ClamAV
Product
Cisco Elastic Services Controller
Classifications
CWE-400, T1499.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 12, 2024Record 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=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Elastic Services Controllerversion=n/a

Published CVSS scores

5.3Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS: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.

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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 exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.001OS Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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