CVE-2026-72347
Received Received - Intake

xt_connmark Target Invalid Shift Parameters Validation Bypass

Publication date: 2026-08-15

Last updated on: 2026-08-15

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: xt_connmark: reject invalid shift parameters Revision 2 of the CONNMARK target accepts user-controlled shift parameters and applies them to 32-bit mark values in connmark_tg_shift(). A shift_bits value of 32 or more triggers an undefined-shift bug when the rule is evaluated. Invalid shift_dir values are also accepted and silently fall back to the left-shift path. Reject invalid revision-2 shift parameters in connmark_tg_check() so malformed rules fail at installation time, before they can reach the packet path.

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Meta Information

Published
2026-08-15
Last Modified
2026-08-15
Generated
2026-08-15
AI Q&A
2026-08-15
EPSS Evaluated
N/A
NVD
CVE-2026-72347
EUVD
EUVD-2026-59246

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux_kernel linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves the CONNMARK target in netfilter, which incorrectly handles user-controlled shift parameters. When shift_bits is 32 or more, it causes an undefined-shift bug affecting 32-bit mark values. Invalid shift_dir values are also accepted but default to left-shift. The fix rejects invalid revision-2 shift parameters during rule installation to prevent packet path issues.

Impact Analysis

This vulnerability could allow attackers to trigger undefined behavior in the Linux kernel by crafting malicious netfilter rules. This might lead to system crashes, denial-of-service conditions, or potential privilege escalation if exploited. Systems using affected kernel versions with CONNMARK rules are at risk.

Mitigation Strategies

Update the Linux kernel to the latest patched version to resolve the undefined-shift bug in the CONNMARK target. Ensure all netfilter rules using revision 2 of the CONNMARK target are reviewed and validated to prevent invalid shift parameters from being applied.

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