CVE-2026-63887Network attack vector

Pre-authentication kernel code execution via iSCSI overflow

Published Jul 19, 2026 · Updated Jul 19, 2026

Heap buffer overflow in the Linux Kernel LIO iSCSI target allows remote attackers to execute kernel code via crafted Login PDUs. iscsi_encode_text_output uses three unbounded sprintf calls to expand unknown login keys into an 8 KiB response buffer, producing up to about 32 KiB of output. An exposed LIO iSCSI target portal is required; the pre-authentication overwrite permits kernel memory disclosure or modification, code execution, or a host crash.

CVSS severity9.8
Critical
EPSS probability0.78%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in the Linux Kernel LIO iSCSI target allows remote attackers to execute kernel code via crafted Login PDUs. iscsi_encode_text_output uses three unbounded sprintf calls to expand unknown login keys into an 8 KiB response buffer, producing up to about 32 KiB of output. An exposed LIO iSCSI target portal is required; the pre-authentication overwrite permits kernel memory disclosure or modification, code execution, or a host crash.

The record

CVE
CVE-2026-63887
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

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=3.1
  2. Affected versionversion=e48354ce078c079996f89d715dfa44814b4eba01 <26e4a304b7e6f1338c675d527608d32549c091db
  3. Affected versionversion=e48354ce078c079996f89d715dfa44814b4eba01 <30bf335e8fe170322080ee001f05ca29c50680b3
  4. Affected versionversion=e48354ce078c079996f89d715dfa44814b4eba01 <4e9f0c4a645c995bc75c06c7b3644254ffb4c76b
  5. Affected versionversion=e48354ce078c079996f89d715dfa44814b4eba01 <594a40360012ce5f94c715d5e3b20fa3af7d525a
  6. Affected versionversion=e48354ce078c079996f89d715dfa44814b4eba01 <b19382dfc6e7dee6d3859ba44b6ca29e97a51627
  7. Affected versionversion=e48354ce078c079996f89d715dfa44814b4eba01 <bf33e01f88388c43e285492a63e539df6ffed64c
  8. Affected versionversion=e48354ce078c079996f89d715dfa44814b4eba01 <cb84e974fb172bc71386289f37b78ea679410b39
  9. Affected versionversion=e48354ce078c079996f89d715dfa44814b4eba01 <efe633e600a0ac68357206fede21b1ac8178f3b8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=3.1; version=e48354ce078c079996f89d715dfa44814b4eba01 <26e4a304b7e6f1338c675d527608d32549c091db; version=e48354ce078c079996f89d715dfa44814b4eba01 <30bf335e8fe170322080ee001f05ca29c50680b3; version=e48354ce078c079996f89d715dfa44814b4eba01 <4e9f0c4a645c995bc75c06c7b3644254ffb4c76b; version=e48354ce078c079996f89d715dfa44814b4eba01 <594a40360012ce5f94c715d5e3b20fa3af7d525a; version=e48354ce078c079996f89d715dfa44814b4eba01 <b19382dfc6e7dee6d3859ba44b6ca29e97a51627; version=e48354ce078c079996f89d715dfa44814b4eba01 <bf33e01f88388c43e285492a63e539df6ffed64c; version=e48354ce078c079996f89d715dfa44814b4eba01 <cb84e974fb172bc71386289f37b78ea679410b39; version=e48354ce078c079996f89d715dfa44814b4eba01 <efe633e600a0ac68357206fede21b1ac8178f3b8

Published CVSS scores

9.8kernel.orgCVSS:3.1/AV:N/AC:L/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

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

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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