CVE-2026-53223 Linux CVE debrief

Who should care

System administrators and security teams responsible for Linux kernel-based systems should be aware of this vulnerability. Given its HIGH severity and potential impact on data confidentiality, affected organizations should prioritize patching. The vulnerability's exploitation requires local access and low privileges, making it a significant concern for multi-user environments.

Technical summary

The CVE-2026-53223 vulnerability is caused by incorrect handling of PACKET_OUTGOING markers in skbs (socket buffer packets) within the Linux kernel's networking subsystem. The kernel's generic timestamp cmsg path can incorrectly read AF_PACKET control-buffer state as sock_exterr_skb::opt_stats, potentially leading to information disclosure or triggering hardened usercopy protections. This issue arises from the incorrect assumption that PACKET_OUTGOING is the sole marker for an skb from sk_error_queue. The vulnerability has been resolved by making skb_is_err_queue() verify that the PACKET_OUTGOING marker is paired with the sock_rmem_free destructor installed by sock_queue_err_skb().

Defensive priority

This vulnerability has a HIGH CVSS score of 7.1 and could lead to information disclosure. Affected organizations should prioritize patching to prevent potential exploitation.

Recommended defensive actions

• Apply the official patch from the Linux kernel maintainers to update the kernel to a version that includes the fix.
• Review system logs for any suspicious activity related to network packet handling.
• Implement additional monitoring of system calls related to socket operations.
• Consider temporarily disabling timestamping for error queue skbs if patching is not immediately feasible.
• Inventory Linux kernel-based systems and prioritize patching based on system criticality and exposure.

Evidence notes

The CVE-2026-53223 vulnerability was introduced due to incorrect handling of PACKET_OUTGOING markers in skbs within the Linux kernel's networking subsystem. The vulnerability allows for potential information disclosure or triggering of hardened usercopy protections. The issue has been resolved by updating the skb_is_err_queue() function to verify the PACKET_OUTGOING marker and sock_rmem_free destructor pairing.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.