CVE-2026-63889

Kernel-memory disclosure and hang via FPIN wraparound

Published Jul 19, 2026 · Updated Jul 19, 2026

Integer overflow in the Linux Kernel FC transport allows attackers to disclose kernel memory and hang the host via crafted FPIN frames. The Link-Integrity and Peer-Congestion walkers compare an 8-bit counter with the 32-bit pname_count field without bounding it to the validated descriptor, so 256 wraps the counter and reads beyond the descriptor indefinitely. Reachability requires an lpfc or qla2xxx initiator and an adjacent fabric actor able to inject FPIN ELS traffic; the loop can disclose adjacent kernel memory and soft-lock the host.

CVSS severity8.1
High
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in the Linux Kernel FC transport allows attackers to disclose kernel memory and hang the host via crafted FPIN frames. The Link-Integrity and Peer-Congestion walkers compare an 8-bit counter with the 32-bit pname_count field without bounding it to the validated descriptor, so 256 wraps the counter and reads beyond the descriptor indefinitely. Reachability requires an lpfc or qla2xxx initiator and an adjacent fabric actor able to inject FPIN ELS traffic; the loop can disclose adjacent kernel memory and soft-lock the host.

The record

CVE
CVE-2026-63889
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499
Attack vector
adjacent
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=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <07776b7779c9426982c1ad74aad91bd531593790
  2. Affected versionversion=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <163bd704d7515c3df6c2e03bcba93d1db79edbff
  3. Affected versionversion=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <29f126f09e34a425b376b3646c89aa7cc18b142c
  4. Affected versionversion=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <35461d23744175a78b6280293892cca357c22793
  5. Affected versionversion=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <a9a39233ec1fc9f97ea1340a4d09bb7ec2be5153
  6. Affected versionversion=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <bdff76dff6ec23d6fe35812fa33e5c4ce2cdb770
  7. Affected versionversion=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <ee57b89e5da9fffbe0d26647e4ff0750dacb9943
  8. Affected versionversion=5.11

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <07776b7779c9426982c1ad74aad91bd531593790; version=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <163bd704d7515c3df6c2e03bcba93d1db79edbff; version=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <29f126f09e34a425b376b3646c89aa7cc18b142c; version=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <35461d23744175a78b6280293892cca357c22793; version=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <a9a39233ec1fc9f97ea1340a4d09bb7ec2be5153; version=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <bdff76dff6ec23d6fe35812fa33e5c4ce2cdb770; version=3dcfe0de5a9752e646a61f4ce513ac059960c7c3 <ee57b89e5da9fffbe0d26647e4ff0750dacb9943; version=5.11

Published CVSS scores

8.1Linux kernel CNACVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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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