Bug 2419842 (CVE-2025-40279)

Summary: CVE-2025-40279 kernel: Linux kernel: Information disclosure via uninitialized data in tcf_connmark_dump()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in the Linux kernel. A local user could exploit a vulnerability in the `tcf_connmark_dump()` function, where a partially initialized structure leads to uninitialized padding bytes being copied into a netlink message. This information disclosure could allow an attacker to gain access to sensitive kernel memory contents.
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Description OSIDB Bzimport 2025-12-08 07:02:43 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net: sched: act_connmark: initialize struct tc_ife to fix kernel leak

In tcf_connmark_dump(), the variable 'opt' was partially initialized using a
designatied initializer. While the padding bytes are reamined
uninitialized. nla_put() copies the entire structure into a
netlink message, these uninitialized bytes leaked to userspace.

Initialize the structure with memset before assigning its fields
to ensure all members and padding are cleared prior to beign copied.
Comment 1 Alexander B 2025-12-10 10:49:29 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025120717-CVE-2025-40279-81d3@gregkh/T