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CVE Record

CVE-2021-47369: s390/qeth: fix NULL deref in qeth_clear_working_pool_list()

In the Linux kernel, the following vulnerability has been resolved: s390/qeth: fix NULL deref in qeth_clear_working_pool_list() When qeth_set_online() calls qeth_clear_working_pool_list() to roll back after an error exit from qeth_hardsetup_card(), we are at risk of accessing card->qdio.in_q before it was allocated by qeth_alloc_qdio_queues() via qeth_mpc_initialize(). qeth_clear_working_pool_list() then dereferences NULL, and by writing to queue->bufs[i].pool_entry scribbles all over the CPU's lowcore. Resulting in a crash when those lowcore areas are used next (eg. on the next machine-check interrupt). Such a scenario would typically happen when the device is first set online and its queues aren't allocated yet. An early IO error or certain misconfigs (eg. mismatched transport mode, bad portno) then cause us to error out from qeth_hardsetup_card() with card->qdio.in_q still being NULL. Fix it by checking the pointer for NULL before accessing it. Note that we also have (rare) paths inside qeth_mpc_initialize() where a configuration change can cause us to free the existing queues, expecting that subsequent code will allocate them again. If we then error out before that re-allocation happens, the same bug occurs. Root-caused-by: Heiko Carstens <hca@linux.ibm.com>

MediumCVSS 5.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel crash bug in IBM s390 qeth networking. If triggered locally during device setup or certain configuration errors, the kernel can dereference a NULL pointer and crash. The business impact is availability loss on affected s390 Linux systems, not data theft or remote compromise based on the supplied sources.

Executive priority

Prioritize for IBM Z or LinuxONE environments where s390 qeth networking is used, especially production systems requiring high uptime. It is lower urgency for environments without s390 Linux, qeth devices, or local administrative access paths.

Technical view

The qeth driver can call qeth_clear_working_pool_list() before card->qdio.in_q is allocated, or after queues are freed and not reallocated. The function then dereferences NULL and writes through queue buffer state, corrupting lowcore and causing a later crash. The fix adds a NULL check before access.

Likely exposure

Exposure appears limited to Linux on s390 systems using the qeth network driver. The CVE uses local attack vector, low privileges, no user interaction, and high availability impact. Internet-facing exposure is not indicated by the provided sources.

Exploitation context

The source bundle does not show active exploitation, and KEV is false. Trigger conditions described are early I/O errors or misconfiguration when a qeth device is first set online, or rare queue reallocation paths during configuration changes.

Researcher notes

The vulnerability is CWE-476 and CVSS 5.5. The primary uncertainty is exact affected version mapping because the bundle lists kernel versions and commits without full distro backport status. Treat vendor package guidance as authoritative for exposure decisions.

Mitigation direction

  • Apply vendor kernel updates containing the referenced stable qeth fixes.
  • Confirm your distribution has backported the fix if kernel versions differ.
  • Restrict local access to network device administration on s390 systems.
  • Review qeth transport mode and port configuration for known misconfigurations.

Validation and detection

  • Inventory Linux s390 hosts using the qeth driver.
  • Compare installed kernel packages with vendor advisories or stable fix commits.
  • Check kernel logs for qeth setup errors or crash signatures around device online operations.
  • Validate qeth device online transitions in staging after patching.
Prepared
Confidence
high
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-476: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-47369 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
2ADP providers
4Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.5CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H1.83.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

5.5Medium
CVSS 3.1 vector shape for CVE-2021-47369Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxeff73e16ee116f6eafa2be48fab42659a27cb453, eff73e16ee116f6eafa2be48fab42659a27cb453, eff73e16ee116f6eafa2be48fab42659a27cb453, b2400fe7e1011c5f3dc2268e8382082465b1c8a2, 22697ca855c06a4a1264d5651542b7d98870a8c4unaffected
LinuxLinux5.9, 0, 5.10.70, 5.14.9, 5.15affected
Weakness

CWE details

CWE-476

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-476 · source CWE mapping

NULL Pointer Dereference

NULL Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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