What’s Vulnerable › Vulnerabilities

CVE-2025-59089: Python-kdcproxy: remote dos via unbounded tcp upstream buffering

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.

Affected products

How to fix

Upgrade to a fixed version: latchset kdcproxy 1.1.0; Red Hat Enterprise Linux 10 0:1.0.0-19.el10_1; Red Hat Enterprise Linux 10.0 Extended Update Support 0:1.0.0-19.el10_0; Red Hat Enterprise Linux 7 Extended Lifecycle Support 0:0.3.2-3.el7_9.3; Red Hat Enterprise Linux 8 8100020251028161822.823393f5, 8100020251103113748.143e9e98; Red Hat Enterprise Linux 8.2 Advanced Update Support 8020020251106022345.792f4060; Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 8040020251103205102.5b01ab7e; Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 8040020251103205102.5b01ab7e; Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support 8060020251030180424.ada582f1; Red Hat Enterprise Linux 8.6 Telecommunications Update Service 8060020251030180424.ada582f1; Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions 8060020251030180424.ada582f1; Red Hat Enterprise Linux 8.8 Telecommunications Update Service 8080020251029082621.b0a6ceea. Check the vendor advisory for mitigations.

References

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