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CVE Record

CVE-2021-29534: CHECK-fail in SparseConcat

TensorFlow is an end-to-end open source platform for machine learning. An attacker can trigger a denial of service via a `CHECK`-fail in `tf.raw_ops.SparseConcat`. This is because the implementation(https://github.com/tensorflow/tensorflow/blob/b432a38fe0e1b4b904a6c222cbce794c39703e87/tensorflow/core/kernels/sparse_concat_op.cc#L76) takes the values specified in `shapes[0]` as dimensions for the output shape. The `TensorShape` constructor(https://github.com/tensorflow/tensorflow/blob/6f9896890c4c703ae0a0845394086e2e1e523299/tensorflow/core/framework/tensor_shape.cc#L183-L188) uses a `CHECK` operation which triggers when `InitDims`(https://github.com/tensorflow/tensorflow/blob/6f9896890c4c703ae0a0845394086e2e1e523299/tensorflow/core/framework/tensor_shape.cc#L212-L296) returns a non-OK status. This is a legacy implementation of the constructor and operations should use `BuildTensorShapeBase` or `AddDimWithStatus` to prevent `CHECK`-failures in the presence of overflows. The fix will be included in TensorFlow 2.5.0. We will also cherrypick this commit on TensorFlow 2.4.2, TensorFlow 2.3.3, TensorFlow 2.2.3 and TensorFlow 2.1.4, as these are also affected and still in supported range.

LowCVSS 2.5Not KEV-listedUpdated
Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

This is a low-severity TensorFlow denial-of-service issue. A user who can run TensorFlow code locally with crafted SparseConcat inputs may trigger an internal CHECK failure, causing a process crash rather than data theft or code execution. Business urgency is usually low unless TensorFlow runs untrusted jobs in shared or production ML infrastructure.

Executive priority

Handle through standard dependency maintenance. Prioritize sooner for multi-tenant ML platforms, hosted notebook environments, or production systems that run user-supplied TensorFlow workloads where a crash could affect other customers or critical processing.

Technical view

CVE-2021-29534 affects TensorFlow SparseConcat. The implementation derives the output shape from shapes[0], and legacy TensorShape construction can CHECK-fail when dimension initialization returns a non-OK status, including overflow cases. The result is availability impact only. Vendor fixes were planned for TensorFlow 2.5.0 and cherry-picked to supported 2.4.2, 2.3.3, 2.2.3, and 2.1.4.

Likely exposure

Exposure is limited to systems running affected TensorFlow versions before the patched releases, especially where users can submit models, notebooks, training jobs, or ML workloads that invoke SparseConcat. Standalone applications using fixed trusted models are less likely to be practically exposed.

Exploitation context

The CVSS vector is local, high complexity, low privileges, no user interaction, with low availability impact. The source bundle does not cite KEV listing, public exploitation, or remote exploitation. Treat exploitation evidence as incomplete beyond the vendor-described crash condition.

Researcher notes

This maps to CWE-754 and centers on unsafe error handling in legacy TensorShape construction. The vendor description indicates operations should avoid CHECK-failures by using status-returning shape construction APIs. Evidence supports denial of service only; do not infer confidentiality, integrity, remote attack, or code execution impact.

Mitigation direction

  • Upgrade TensorFlow to 2.5.0 or a patched supported branch release.
  • Use 2.4.2, 2.3.3, 2.2.3, or 2.1.4 where pinned to older branches.
  • Check TensorFlow vendor advisory for branch-specific guidance.
  • Restrict untrusted ML jobs from shared production workers where practical.
  • Monitor TensorFlow worker crashes during training or inference workloads.

Validation and detection

  • Inventory TensorFlow versions in applications, containers, notebooks, and build locks.
  • Confirm no deployed dependency matches the affected version ranges.
  • Review whether users can submit untrusted models or TensorFlow jobs.
  • Search code and model pipelines for SparseConcat usage.
  • Run normal regression tests after upgrading TensorFlow.
Prepared
Confidence
high
Sources
4

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-754: Exact CWE lookup

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Open ATT&CK lookup
cve · low confidence lookup

CVE-2021-29534 mapping review

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Vulnerability profileCVE Program record
Severity
Low
CVSS
2.5 (3.1)
Known Exploited
No
Published

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

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
0Timeline events
0ADP providers
3Source links

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
2.5CVSS 3.1LowCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L11.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

2.5Low
CVSS 3.1 vector shape for CVE-2021-29534Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

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

Products and packages named in the record

VendorProductVersion / packageStatus
tensorflowtensorflow< 2.1.4, >= 2.2.0, < 2.2.3, >= 2.3.0, < 2.3.3, >= 2.4.0, < 2.4.2Listed
Weakness

CWE details

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

CWE-754 · source CWE mapping

Improper Check for Unusual or Exceptional Conditions

Improper Check for Unusual or Exceptional Conditions represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.