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CVE Record

CVE-2021-37676: Reference binding to nullptr in shape inference in TensorFlow

TensorFlow is an end-to-end open source platform for machine learning. In affected versions an attacker can cause undefined behavior via binding a reference to null pointer in `tf.raw_ops.SparseFillEmptyRows`. The shape inference [implementation](https://github.com/tensorflow/tensorflow/blob/460e000de3a83278fb00b61a16d161b1964f15f4/tensorflow/core/ops/sparse_ops.cc#L608-L634) does not validate that the input arguments are not empty tensors. We have patched the issue in GitHub commit 578e634b4f1c1c684d4b4294f9e5281b2133b3ed. 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

TensorFlow versions in the affected ranges can behave unsafely when a specific sparse-tensor operation receives empty tensor inputs. In systems where a lower-privileged user can run TensorFlow workloads or influence tensors reaching that operation, this could affect confidentiality, integrity, or availability. Sources do not show active exploitation.

Executive priority

Prioritize patching where TensorFlow is used in shared ML infrastructure or user-facing data-processing services. The issue is high severity, but the supplied evidence points to local or workload-level access rather than unauthenticated remote exploitation.

Technical view

CVE-2021-37676 is a TensorFlow undefined-behavior flaw in shape inference for `tf.raw_ops.SparseFillEmptyRows`. The implementation failed to validate non-empty input tensors, allowing a reference to bind to a null pointer. The advisory rates it CVSS 7.8 with local attack vector and low privileges required.

Likely exposure

Exposure is most likely in ML platforms, notebooks, batch jobs, or services running affected TensorFlow releases where untrusted or lower-privileged users can execute TensorFlow operations or influence tensor inputs. The listed affected ranges are TensorFlow 2.5.0 before 2.5.1, 2.4.x before 2.4.3, and versions before 2.3.4.

Exploitation context

The public sources describe local, low-privilege exploitation potential and no required user interaction. They do not provide evidence of internet-scale exploitation, known malware use, or CISA KEV listing. Treat exploitation status as unconfirmed from the supplied evidence.

Researcher notes

The core issue is missing empty-tensor validation in TensorFlow sparse operation shape inference. The vendor identified the fix commit and target fixed releases. The sources do not name a workaround beyond upgrading, and they do not establish exploitation in the wild.

Mitigation direction

  • Upgrade TensorFlow to 2.6.0 or a fixed supported release.
  • For 2.5.x, update to TensorFlow 2.5.1 or later.
  • For 2.4.x, update to TensorFlow 2.4.3 or later.
  • For 2.3.x or older, update to TensorFlow 2.3.4 or a newer fixed release.
  • Restrict untrusted users from running arbitrary TensorFlow workloads until patched.

Validation and detection

  • Inventory TensorFlow versions in applications, notebooks, containers, and ML images.
  • Confirm deployed versions are outside the affected ranges listed by the advisory.
  • Review code paths using `tf.raw_ops.SparseFillEmptyRows` with untrusted inputs.
  • Verify patched builds include commit `578e634b4f1c1c684d4b4294f9e5281b2133b3ed`.
  • Record no active exploitation evidence unless new trusted sources show otherwise.
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-824: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-37676 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
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
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-2021-37676Attack 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-824 · source CWE mapping

Access of Uninitialized Pointer

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