CVE-2026-99191Public exploit

Packet-length corruption via CALIPSO BIG TCP arithmetic

Published Oct 28, 2026 · Updated Oct 28, 2026

Length corruption in Linux CALIPSO allows attackers to trigger incorrect IPv6 packet-length handling via BIG TCP traffic. calipso_skbuff_setattr() adds an option-length delta to the 16-bit payload_len field, replacing BIG TCP's zero sentinel or wrapping at the size boundary. Exposure requires CALIPSO labeling of affected aggregated packets; downstream length consumers receive incorrect values, but the disclosure establishes no crash or policy bypass.

CVSS severityUnavailable
Unscored
EPSS probability0.17%
Next 30 days · Nov 1, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Length corruption in Linux CALIPSO allows attackers to trigger incorrect IPv6 packet-length handling via BIG TCP traffic. calipso_skbuff_setattr() adds an option-length delta to the 16-bit payload_len field, replacing BIG TCP's zero sentinel or wrapping at the size boundary. Exposure requires CALIPSO labeling of affected aggregated packets; downstream length consumers receive incorrect values, but the disclosure establishes no crash or policy bypass.

The record

CVE
CVE-2026-99191
Published
Oct 28, 2026
Updated
Oct 28, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Oct 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 28, 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=5.19
  2. Affected versionversion=81fbc812132cbc72a0f933b19bfd3a829bd946e4 <1c9fcfca51e3c5cd46dd72a4da74d56eff183513
  3. Affected versionversion=81fbc812132cbc72a0f933b19bfd3a829bd946e4 <8070ed578b6b9134e045627fb745c887a806d46e
  4. Affected versionversion=81fbc812132cbc72a0f933b19bfd3a829bd946e4 <8ee0e03663826a76507048d58466b29321a57656

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=5.19; version=81fbc812132cbc72a0f933b19bfd3a829bd946e4 <1c9fcfca51e3c5cd46dd72a4da74d56eff183513; version=81fbc812132cbc72a0f933b19bfd3a829bd946e4 <8070ed578b6b9134e045627fb745c887a806d46e; version=81fbc812132cbc72a0f933b19bfd3a829bd946e4 <8ee0e03663826a76507048d58466b29321a57656

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.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

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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