CVE-2026-17255

Service interruption via unchecked ICMPv6 prefix length

Published Sep 4, 2026 · Updated Sep 4, 2026

Out-of-bounds write in IBMi 7.3 through 7.6 allows remote attackers to interrupt service via crafted ICMPv6 Router Advertisements. The ICMPv6 Router Advertisement handler fails to validate an advertised prefix length before using it in a memory write. The condition is reachable without authentication or user interaction from an adjacent network and can disrupt availability; IBM has not specified whether it causes a hang, crash, or reboot.

CVSS severity4.3
Medium
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in IBMi 7.3 through 7.6 allows remote attackers to interrupt service via crafted ICMPv6 Router Advertisements. The ICMPv6 Router Advertisement handler fails to validate an advertised prefix length before using it in a memory write. The condition is reachable without authentication or user interaction from an adjacent network and can disrupt availability; IBM has not specified whether it causes a hang, crash, or reboot.

The record

CVE
CVE-2026-17255
Published
Sep 4, 2026
Updated
Sep 4, 2026
Vendor
IBM
Product
IBM i
Classifications
CWE-787, T1499
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 4, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 4, 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=7.3
  2. Affected versionversion=7.4
  3. Affected versionversion=7.5
  4. Affected versionversion=7.6

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

IBM · IBM iversion=7.3; version=7.4; version=7.5; version=7.6

Published CVSS scores

4.3IBMCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/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.

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

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499Endpoint 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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