CVE-2026-63868

GARP receive-path disruption via unsigned length underflow

Published Jul 19, 2026 · Updated Jul 19, 2026

Unsigned integer underflow in the Linux Kernel GARP parser allows attackers to disrupt dynamic VLAN registration via crafted attributes. In garp_pdu_parse_attr, reversed operands subtract the untrusted on-wire ga->len from the header size; unsigned wraparound is then truncated to u8 before garp_attr_lookup compares it. The host must process GARP traffic for locally registered attributes, and the mismatch causes received Join and Leave events to be ignored rather than crashing the kernel.

CVSS severityUnavailable
Unscored
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unsigned integer underflow in the Linux Kernel GARP parser allows attackers to disrupt dynamic VLAN registration via crafted attributes. In garp_pdu_parse_attr, reversed operands subtract the untrusted on-wire ga->len from the header size; unsigned wraparound is then truncated to u8 before garp_attr_lookup compares it. The host must process GARP traffic for locally registered attributes, and the mismatch causes received Join and Leave events to be ignored rather than crashing the kernel.

The record

CVE
CVE-2026-63868
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1498
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.6.27
  2. Affected versionversion=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <04e22fefac1af3e32f245e9045382348773b5d59
  3. Affected versionversion=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <16e408e607a94b646fb14a2a98422c6877ae4b3c
  4. Affected versionversion=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <29f28172afb2ae7b31e9bf3e978396f20b381688
  5. Affected versionversion=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <74e02121be1dcc0efcd56ebdf0171d6129105659
  6. Affected versionversion=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <973cf7c433d27f4d9556d0b7c332543be7ed7a6e
  7. Affected versionversion=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <a11f1a671b1361f0f1278dc0041374f2730df73f
  8. Affected versionversion=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <d4c86ea09ae3e63ee5aa86e941fcc38e0e39874a
  9. Affected versionversion=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <d8dcd14aa886b8effd83022c550669f4f262854b

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=2.6.27; version=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <04e22fefac1af3e32f245e9045382348773b5d59; version=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <16e408e607a94b646fb14a2a98422c6877ae4b3c; version=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <29f28172afb2ae7b31e9bf3e978396f20b381688; version=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <74e02121be1dcc0efcd56ebdf0171d6129105659; version=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <973cf7c433d27f4d9556d0b7c332543be7ed7a6e; version=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <a11f1a671b1361f0f1278dc0041374f2730df73f; version=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <d4c86ea09ae3e63ee5aa86e941fcc38e0e39874a; version=eca9ebac651f774d8b10fce7c5d173c3c3d3394f <d8dcd14aa886b8effd83022c550669f4f262854b

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1498Network Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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