Linux Kernel up to 7.0.12 Garp Attribute Parser net/ipv4/garp.c garp_pdu_parse_attr len integer underflow

Summaryinfo

A vulnerability has been found in Linux Kernel up to 7.0.12 and classified as critical. Affected by this vulnerability is the function garp_pdu_parse_attr of the file net/ipv4/garp.c of the component Garp Attribute Parser. Performing a manipulation of the argument len results in integer underflow. This vulnerability was named CVE-2026-63868. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 7.0.12. This affects the function garp_pdu_parse_attr of the file net/ipv4/garp.c of the component Garp Attribute Parser. The manipulation of the argument len with an unknown input leads to a integer underflow vulnerability. CWE is classifying the issue as CWE-191. The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result. This is going to have an impact on availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: net: garp: fix unsigned integer underflow in garp_pdu_parse_attr The receive-side GARP attribute parser computes dlen with reversed operands: dlen = sizeof(*ga) - ga->len; ga->len is the on-wire attribute length and includes the GARP attribute header. For normal attributes with data, ga->len is larger than sizeof(*ga), so the subtraction underflows in unsigned arithmetic. The resulting value is later passed to garp_attr_lookup(), whose length argument is u8. After truncation, the parsed data length usually no longer matches the length stored for locally registered attributes, so received Join/Leave events are ignored. This breaks the GARP receive path for common attributes, such as GVRP VLAN registration attributes. Compute the data length as the attribute length minus the header length.

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-63868 since 07/19/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 07/19/2026).

Upgrading to version 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36 or 7.0.13 eliminates this vulnerability.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 5.10.258
• 5.15.209
• 6.1.175
• 6.6.142
• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
• 6.12.6
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• 6.12.87
• 6.12.88
• 6.12.89
• 6.12.90
• 6.12.91
• 6.12.92
• 6.12.93
• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
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• 6.18.29
• 6.18.30
• 6.18.31
• 6.18.32
• 6.18.33
• 6.18.34
• 6.18.35
• 7.0.0
• 7.0.1
• 7.0.2
• 7.0.3
• 7.0.4
• 7.0.5
• 7.0.6
• 7.0.7
• 7.0.8
• 7.0.9
• 7.0.10
• 7.0.11
• 7.0.12

License

• open-source

Website

• Vendor: https://www.kernel.org/

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