CVE-2026-63886Network attack vector

Pre-auth kernel memory corruption via CHAP response

Published Jul 19, 2026 · Updated Jul 19, 2026

Heap overflow in the Linux Kernel allows remote attackers to corrupt kernel memory through crafted iSCSI CHAP authentication responses. In chap_server_compute_hash(), the BASE64 branch passes CHAP_R to chap_base64_decode() before confirming that the decoded output fits client_digest. A reachable in-kernel iSCSI target with CHAP enabled and a known configured username is required; the overwrite can crash the kernel or enable kernel-level code execution.

CVSS severity9.8
Critical
EPSS probability0.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap overflow in the Linux Kernel allows remote attackers to corrupt kernel memory through crafted iSCSI CHAP authentication responses. In chap_server_compute_hash(), the BASE64 branch passes CHAP_R to chap_base64_decode() before confirming that the decoded output fits client_digest. A reachable in-kernel iSCSI target with CHAP enabled and a known configured username is required; the overwrite can crash the kernel or enable kernel-level code execution.

The record

CVE
CVE-2026-63886
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1210
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

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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=1e5733883421495908f3b90d9d807663038b4136 <4a3a19c98a8207ad08bec554703d90f2c34a8cc6
  2. Affected versionversion=1e5733883421495908f3b90d9d807663038b4136 <82454e6f21e56ea9a0a9de7d0ff7e1dfb83e34d6
  3. Affected versionversion=1e5733883421495908f3b90d9d807663038b4136 <85db7391310b1304d2dc8ae3b0b12105a9567147
  4. Affected versionversion=1e5733883421495908f3b90d9d807663038b4136 <bf154c657828ed05399bca5d98cf1611bb048b12
  5. Affected versionversion=1e5733883421495908f3b90d9d807663038b4136 <c04e85799356120209b351a148ac2db888d5ffd9
  6. Affected versionversion=1e5733883421495908f3b90d9d807663038b4136 <edd06675a02376ea8347dba7c29ad982ba5b36ee
  7. Affected versionversion=6.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=1e5733883421495908f3b90d9d807663038b4136 <4a3a19c98a8207ad08bec554703d90f2c34a8cc6; version=1e5733883421495908f3b90d9d807663038b4136 <82454e6f21e56ea9a0a9de7d0ff7e1dfb83e34d6; version=1e5733883421495908f3b90d9d807663038b4136 <85db7391310b1304d2dc8ae3b0b12105a9567147; version=1e5733883421495908f3b90d9d807663038b4136 <bf154c657828ed05399bca5d98cf1611bb048b12; version=1e5733883421495908f3b90d9d807663038b4136 <c04e85799356120209b351a148ac2db888d5ffd9; version=1e5733883421495908f3b90d9d807663038b4136 <edd06675a02376ea8347dba7c29ad982ba5b36ee; version=6.0

Published CVSS scores

9.8UbuntuCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.0Oracle LinuxCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
9.8Linux kernel CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5Amazon LinuxCVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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

T1210Exploitation of Remote Services

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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