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CVE Record

CVE-2021-37665: Incomplete validation in MKL requantization in TensorFlow

TensorFlow is an end-to-end open source platform for machine learning. In affected versions due to incomplete validation in MKL implementation of requantization, an attacker can trigger undefined behavior via binding a reference to a null pointer or can access data outside the bounds of heap allocated arrays. The [implementation](https://github.com/tensorflow/tensorflow/blob/460e000de3a83278fb00b61a16d161b1964f15f4/tensorflow/core/kernels/mkl/mkl_requantization_range_per_channel_op.cc) does not validate the dimensions of the `input` tensor. A similar issue occurs in `MklRequantizePerChannelOp`. The [implementation](https://github.com/tensorflow/tensorflow/blob/460e000de3a83278fb00b61a16d161b1964f15f4/tensorflow/core/kernels/mkl/mkl_requantize_per_channel_op.cc) does not perform full validation for all the input arguments. We have patched the issue in GitHub commit 9e62869465573cb2d9b5053f1fa02a81fce21d69 and in the Github commit 203214568f5bc237603dbab6e1fd389f1572f5c9. The fix will be included in TensorFlow 2.6.0. We will also cherrypick this commit on TensorFlow 2.5.1, TensorFlow 2.4.3, and TensorFlow 2.3.4, as these are also affected and still in supported range.

HighCVSS 7.8Not KEV-listedUpdated
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2021-37665 is a TensorFlow input-validation flaw in MKL requantization code. A low-privileged local attacker may trigger undefined behavior or out-of-bounds heap access, potentially affecting confidentiality, integrity, and availability. It matters most on shared ML systems where users can run or influence TensorFlow workloads.

Executive priority

Treat as high priority for shared or production ML environments using affected TensorFlow releases. The issue is not reported as actively exploited, but the impact rating is high and fixed releases are available, so remediation should be scheduled promptly through normal dependency update channels.

Technical view

Affected TensorFlow versions fail to fully validate input tensor dimensions and arguments in MKL requantization per-channel operations. The advisory describes null pointer reference binding and heap out-of-bounds access. CVSS 3.1 is 7.8, local attack vector, low complexity, low privileges, no user interaction, high CIA impact.

Likely exposure

Exposure is likely limited to systems running affected TensorFlow versions with relevant MKL requantization paths reachable by local users or jobs. Shared notebooks, training hosts, and multi-user ML pipelines deserve priority review. Evidence does not support treating this as a general remote network vulnerability.

Exploitation context

The source bundle does not show CISA KEV listing or active exploitation evidence. The CVSS vector indicates local, low-privileged exploitation without user interaction. Practical risk depends on whether an attacker can run or influence TensorFlow code and tensors on the affected system.

Researcher notes

The cited issue is CWE-20 incomplete input validation in TensorFlow MKL requantization implementations. Sources name commits 9e62869465573cb2d9b5053f1fa02a81fce21d69 and 203214568f5bc237603dbab6e1fd389f1572f5c9 as fixes. Avoid assuming exploitability beyond local low-privileged execution without additional environment evidence.

Mitigation direction

  • Upgrade TensorFlow to 2.6.0 or fixed supported branch releases.
  • Use TensorFlow 2.5.1, 2.4.3, or 2.3.4 where branch pinning is required.
  • Prioritize shared ML systems that allow untrusted local TensorFlow jobs.
  • Restrict local job execution to trusted users until affected environments are patched.
  • Check the TensorFlow advisory and commits for branch-specific guidance.

Validation and detection

  • Inventory TensorFlow versions in hosts, notebooks, containers, and lockfiles.
  • Flag versions >=2.5.0 <2.5.1, >=2.4.0 <2.4.3, and <2.3.4.
  • Identify workloads using TensorFlow MKL or Intel-optimized execution paths.
  • Confirm upgraded images and dependency locks no longer include affected versions.
  • Run existing ML and security regression tests after the TensorFlow update.
Prepared
Confidence
high
Sources
5

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-20: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-37665 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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
0Timeline events
0ADP providers
4Source 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
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2021-37665Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Products and packages named in the record

VendorProductVersion / packageStatus
tensorflowtensorflow>= 2.5.0, < 2.5.1, >= 2.4.0, < 2.4.3, < 2.3.4Listed
Weakness

CWE details

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

CWE-20 · source CWE mapping

Improper Input Validation

Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.