Executive Summary

This vulnerability exists in the Linux kernel's netfilter component, specifically in the ctnetlink module. When a netlink message does not include the CTA_EXPECT_NAT field, certain fields (saved_addr and saved_proto) are not initialized properly because the allocation function uses a slab cache that does not zero out memory. As a result, stale data from previous allocations can be leaked to userspace when these fields are checked and emitted incorrectly.

The issue arises because the function ctnetlink_alloc_expect() allocates memory without zeroing it, unlike the safe sibling function nf_ct_expect_init() which explicitly zeroes these fields. This can cause the system to expose leftover data from prior uses, potentially leaking sensitive information.

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Impact Analysis

This vulnerability can lead to the leakage of stale or leftover data from kernel memory to userspace. Since uninitialized fields may contain sensitive information from previous network expectations, an attacker or user with access to the netlink interface could potentially obtain unintended data.

Such leakage could compromise system confidentiality by exposing sensitive network state information, which might be used to infer network configurations or other details that should remain protected.

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