CVE-2025-59089: 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 t...

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.

Metrics

CVSS 3.1

5.9/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.45%

36.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-770

References

Timeline

Published: Nov 12, 2025
Last Modified: Jun 30, 2026
Status: Deferred

Frequently Asked Questions

What is CVE-2025-59089?

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.

How severe is CVE-2025-59089?

CVE-2025-59089 has a CVSS score of 5.9/10 (MEDIUM severity). The EPSS model estimates a 0.45% probability of exploitation in the next 30 days.

How do I fix CVE-2025-59089?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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