Python-kdcproxy: remote dos via unbounded tcp upstream buffering

5.9 CVSS

Vulnerability Description

If an attacker causes kdcproxy to connect to an attacker-controlled KDC server (e.g. through server-side request forgery), they can exploit the fact that kdcproxy does not enforce bounds on TCP response length to conduct a denial-of-service attack. While receiving the KDC's response, kdcproxy copies the entire buffered stream into a new buffer on each recv() call, even when the transfer is incomplete, causing excessive memory allocation and CPU usage. Additionally, kdcproxy accepts incoming response chunks as long as the received data length is not exactly equal to the length indicated in the response header, even when individual chunks or the total buffer exceed the maximum length of a Kerberos message. This allows an attacker to send unbounded data until the connection timeout is reached (approximately 12 seconds), exhausting server memory or CPU resources. Multiple concurrent requests can cause accept queue overflow, denying service to legitimate clients.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

The following person or organization is credited with identifying this vulnerability, as recorded in the NVD database:

Red Hat would like to thank Arad Inbar for reporting this issue.

References

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Affected Vendor

latchset

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Affected Software

kdcproxy, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10.0 Extended Update Support, Red Hat Enterprise Linux 7 Extended Lifecycle Support, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 8.2 Advanced Update Support, Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support, Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On, Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support, Red Hat Enterprise Linux 8.6 Telecommunications Update Service, Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions, Red Hat Enterprise Linux 8.8 Telecommunications Update Service, Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions, Red Hat Enterprise Linux 9, Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions, Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions, Red Hat Enterprise Linux 9.4 Extended Update Support, Red Hat Enterprise Linux 9.6 Extended Update Support

Vulnerable Versions:

0, 0:1.0.0-19.el10_1, 0:1.0.0-19.el10_0, 0:0.3.2-3.el7_9.3, 8100020251103113748.143e9e98, 8100020251028161822.823393f5, 8020020251106022345.792f4060, 8040020251103205102.5b01ab7e, 8060020251030180424.ada582f1, 8080020251029082621.b0a6ceea, 0:1.0.0-9.el9_7, 0:1.0.0-7.el9_0.1, 0:1.0.0-7.el9_2.1, 0:1.0.0-7.el9_4.1, 0:1.0.0-9.el9_6