CVE-2023-41378Public exploitNetwork attack vector

Remote service hang via timeout-free TLS handshake

Published Nov 6, 2023 · Updated Sep 5, 2024

Denial of service in Tigera Calico Typha 3.25.1 and earlier and 3.26.0 through 3.26.2 allows remote attackers to hang the server. The main server accept loop calls TLS Handshake without a timeout, so a client that leaves the handshake incomplete blocks subsequent connections indefinitely. Port 5473 is normally cluster-internal or exposed through a node address, and cluster disruption requires the condition to affect every Typha replica.

CVSS severity7.5
High
EPSS probability0.72%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Tigera Calico Typha 3.25.1 and earlier and 3.26.0 through 3.26.2 allows remote attackers to hang the server. The main server accept loop calls TLS Handshake without a timeout, so a client that leaves the handshake incomplete blocks subsequent connections indefinitely. Port 5473 is normally cluster-internal or exposed through a node address, and cluster disruption requires the condition to affect every Typha replica.

The record

CVE
CVE-2023-41378
Published
Nov 6, 2023
Updated
Sep 5, 2024
Vendor
Tigera
Product
Calico
Classifications
CWE-703, CWE-400, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 6, 2023CVE publishedPublication date reported by the CVE source.
  2. Sep 5, 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=0 <=v3.15.3
  2. Affected versionversion=v3.16.0 <=v3.16.3
  3. Affected versionversion=v3.17.0 <=v3.17.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Tigera · Calicoversion=0 <=v3.15.3; version=v3.16.0 <=v3.16.3; version=v3.17.0 <=v3.17.1
Tigera · Calico Typhaversion=0 <=v3.15.3; version=0 <=v3.25.1; version=v3.16.0 <=v3.16.3; version=v3.17.0 <=v3.17.1; version=v3.26.0 <=v3.26.2

Published CVSS scores

7.5TigeraCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5GitHubCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-703Improper Check or Handling of Exceptional Conditions
CWE-400Uncontrolled Resource Consumption
T1499.002Service Exhaustion Flood

Public exploit references

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

Technologies

Your stack

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Your stack

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