CVE-2026-63830Network attack vector

Page-cache modification via desynchronized ownership bitmap

Published Jul 19, 2026 · Updated Jul 19, 2026

Improper ownership tracking in affected Linux Kernel releases allows attackers to modify file page-cache data through SK_MSG. The sg.copy bitmap becomes desynchronized from msg->sg.data[] when BPF helpers and TLS paths move, split, or compact entries, so externally backed pages are exposed as writable BPF ctx->data. On Ubuntu, exploitation requires CAP_BPF and CAP_NET_ADMIN in the initial user namespace; BPF stores then alter the original page cache.

CVSS severity9.4
Critical
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper ownership tracking in affected Linux Kernel releases allows attackers to modify file page-cache data through SK_MSG. The sg.copy bitmap becomes desynchronized from msg->sg.data[] when BPF helpers and TLS paths move, split, or compact entries, so externally backed pages are exposed as writable BPF ctx->data. On Ubuntu, exploitation requires CAP_BPF and CAP_NET_ADMIN in the initial user namespace; BPF stores then alter the original page cache.

The record

CVE
CVE-2026-63830
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1565.001
Attack vector
network
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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=4.20
  2. Affected versionversion=d3b18ad31f93d0b6bae105c679018a1ba7daa9ca <0eb4c16c4adb262763bda870a8ed38a1a9dec7ec
  3. Affected versionversion=d3b18ad31f93d0b6bae105c679018a1ba7daa9ca <1acdd14c0990dd1cd4b6534f00366d2e6dfce05f
  4. Affected versionversion=d3b18ad31f93d0b6bae105c679018a1ba7daa9ca <21ed9540a8e1906dfcbc1bb82ba9b4de4fa4bd6d
  5. Affected versionversion=d3b18ad31f93d0b6bae105c679018a1ba7daa9ca <406e8a651a7b854c41fecd5117bb282b3a6c2c6b
  6. Affected versionversion=d3b18ad31f93d0b6bae105c679018a1ba7daa9ca <9bb86d8184b37503816150c4a6ad3c17dfdbe827
  7. Affected versionversion=d3b18ad31f93d0b6bae105c679018a1ba7daa9ca <d22cc92bc41290e5783a72375e0843d9435f6001

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=4.20; version=d3b18ad31f93d0b6bae105c679018a1ba7daa9ca <0eb4c16c4adb262763bda870a8ed38a1a9dec7ec; version=d3b18ad31f93d0b6bae105c679018a1ba7daa9ca <1acdd14c0990dd1cd4b6534f00366d2e6dfce05f; version=d3b18ad31f93d0b6bae105c679018a1ba7daa9ca <21ed9540a8e1906dfcbc1bb82ba9b4de4fa4bd6d; version=d3b18ad31f93d0b6bae105c679018a1ba7daa9ca <406e8a651a7b854c41fecd5117bb282b3a6c2c6b; version=d3b18ad31f93d0b6bae105c679018a1ba7daa9ca <9bb86d8184b37503816150c4a6ad3c17dfdbe827; version=d3b18ad31f93d0b6bae105c679018a1ba7daa9ca <d22cc92bc41290e5783a72375e0843d9435f6001

Published CVSS scores

9.4Linux Kernel CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
9.4UbuntuCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1565.001Stored Data Manipulation

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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