CVE-2023-41378: Calico Typha hangs during unclean TLS handshake

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-11-06 · updated 2026-06-17
Weakness: CWE-400

Description

In certain conditions for Calico Typha (v3.26.2, v3.25.1 and below), and Calico Enterprise Typha (v3.17.1, v3.16.3, v3.15.3 and below), a client TLS handshake can block the Calico Typha server indefinitely, resulting in denial of service. The TLS Handshake() call is performed inside the main server handle for loop without any timeout allowing an unclean TLS handshake to block the main loop indefinitely while other connections will be idle waiting for that handshake to finish.

Affected products

Tigera Calico Cloud: before 18.0.0 — fixed in 18.0.0
Tigera Calico Enterprise: before 3.15.4; from 3.16.0 before 3.16.4; from 3.17.0 before 3.17.2 — fixed in 3.15.4, 3.16.4, 3.17.2
Tigera Calico Os: before 3.25.2; from 3.26.0 before 3.26.3 — fixed in 3.25.2, 3.26.3

How to fix

Upgrade to a fixed version: Tigera Calico Cloud 18.0.0; Tigera Calico Enterprise 3.15.4, 3.16.4, 3.17.2; Tigera Calico Os 3.25.2, 3.26.3. Check the vendor advisory for mitigations.

References

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