CVE-2025-21855

Invalid kernel-memory read via post-send skb access

Published Mar 12, 2025 · Updated Aug 5, 2026

Use-after-free in the Linux kernel ibmvnic driver allows attackers to trigger an invalid kernel-memory read during transmission to VIOS. After flushing a transmit buffer, ibmvnic_xmit reads skb->len to update tx_bytes even though a VIOS interrupt can already have freed that skb. The race is especially reachable during live partition mobility; the public record demonstrates a KASAN-detected slab read but no reliable crash or code-execution outcome.

CVSS severity8.6
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the Linux kernel ibmvnic driver allows attackers to trigger an invalid kernel-memory read during transmission to VIOS. After flushing a transmit buffer, ibmvnic_xmit reads skb->len to update tx_bytes even though a VIOS interrupt can already have freed that skb. The race is especially reachable during live partition mobility; the public record demonstrates a KASAN-detected slab read but no reliable crash or code-execution outcome.

The record

CVE
CVE-2025-21855
Published
Mar 12, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Mar 12, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=032c5e82847a2214c3196a90f0aeba0ce252de58 <093b0e5c90592773863f300b908b741622eef597
  2. Affected versionversion=032c5e82847a2214c3196a90f0aeba0ce252de58 <25dddd01dcc8ef3acff964dbb32eeb0d89f098e9
  3. Affected versionversion=032c5e82847a2214c3196a90f0aeba0ce252de58 <501ac6a7e21b82e05207c6b4449812d82820f306
  4. Affected versionversion=032c5e82847a2214c3196a90f0aeba0ce252de58 <abaff2717470e4b5b7c0c3a90e128b211a23da09
  5. Affected versionversion=032c5e82847a2214c3196a90f0aeba0ce252de58 <bdf5d13aa05ec314d4385b31ac974d6c7e0997c9
  6. Affected versionversion=4.5

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=032c5e82847a2214c3196a90f0aeba0ce252de58 <093b0e5c90592773863f300b908b741622eef597; version=032c5e82847a2214c3196a90f0aeba0ce252de58 <25dddd01dcc8ef3acff964dbb32eeb0d89f098e9; version=032c5e82847a2214c3196a90f0aeba0ce252de58 <501ac6a7e21b82e05207c6b4449812d82820f306; version=032c5e82847a2214c3196a90f0aeba0ce252de58 <abaff2717470e4b5b7c0c3a90e128b211a23da09; version=032c5e82847a2214c3196a90f0aeba0ce252de58 <bdf5d13aa05ec314d4385b31ac974d6c7e0997c9; version=4.5

Published CVSS scores

8.6kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
7.8CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/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)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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