Kernel Panic via Uninitialized iovec in ktls_ocf_tls_cbc_decrypt

Executive Summary

This vulnerability involves a flaw in the FreeBSD kernel's TLS 1.2 CBC record handling. When processing received TLS records, the kernel incorrectly increments an index for every mbuf in a chain, including skipped mbufs with only header bytes. This leaves uninitialized entries in the iovec array, which is not zeroed during allocation. A remote attacker can exploit this by controlling TCP segmentation to force the first mbuf to contain only the 5-byte TLS header, causing the kernel to read uninitialized memory during HMAC computation and trigger a kernel panic.

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Detection Guidance

This vulnerability requires specific conditions to trigger, primarily involving TLS 1.2 CBC records with controlled TCP segmentation. Detection may involve monitoring kernel panics or unusual TLS handshake patterns. No direct detection commands are provided in the advisory.

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Impact Analysis

This vulnerability can cause a denial of service (DoS) by crashing the affected system. If exploited, it results in a kernel panic, which would cause the system to reboot or become unresponsive. Systems using FreeBSD with KTLS enabled for TLS 1.2 CBC records are at risk if they process TLS traffic from untrusted sources.

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Compliance Impact

This vulnerability causes kernel panics due to uninitialized memory access during TLS 1.2 CBC record processing, which could lead to service disruptions. Such disruptions may impact availability requirements under GDPR and HIPAA, potentially violating compliance if systems fail to maintain continuous protection of personal or health data.

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Mitigation Strategies

Apply the FreeBSD security patch immediately if running affected versions. Disable KTLS for TLS 1.2 CBC records if patches are unavailable. Monitor FreeBSD security advisories for updates.

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