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CVE Record

CVE-2021-37661: Crash caused by integer conversion to unsigned in TensorFlow

TensorFlow is an end-to-end open source platform for machine learning. In affected versions an attacker can cause a denial of service in `boosted_trees_create_quantile_stream_resource` by using negative arguments. The [implementation](https://github.com/tensorflow/tensorflow/blob/84d053187cb80d975ef2b9684d4b61981bca0c41/tensorflow/core/kernels/boosted_trees/quantile_ops.cc#L96) does not validate that `num_streams` only contains non-negative numbers. In turn, [this results in using this value to allocate memory](https://github.com/tensorflow/tensorflow/blob/84d053187cb80d975ef2b9684d4b61981bca0c41/tensorflow/core/kernels/boosted_trees/quantiles/quantile_stream_resource.h#L31-L40). However, `reserve` receives an unsigned integer so there is an implicit conversion from a negative value to a large positive unsigned. This results in a crash from the standard library. We have patched the issue in GitHub commit 8a84f7a2b5a2b27ecf88d25bad9ac777cd2f7992. 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.

MediumCVSS 5.5Not KEV-listedUpdated
Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

A user who can run TensorFlow code on an affected system can crash a TensorFlow process by supplying negative values to a boosted trees quantile resource operation. This is a denial-of-service issue, not a data theft or code execution issue in the provided sources.

Executive priority

Treat this as a moderate availability risk for shared ML infrastructure. It does not indicate data compromise, but it can disrupt jobs or services if affected TensorFlow workloads are exposed to low-privileged users.

Technical view

The vulnerable TensorFlow kernel failed to validate that num_streams values were non-negative. Negative signed integers were implicitly converted to large unsigned sizes during memory reservation, causing a standard-library crash. The issue is tracked as CWE-681 with CVSS 5.5, local attack vector, low complexity, and low privileges required.

Likely exposure

Exposure is most likely in ML platforms, notebooks, batch jobs, or shared compute environments running affected TensorFlow versions where users can execute TensorFlow workloads. Systems not using TensorFlow, or already on patched releases, are not indicated as affected by the provided sources.

Exploitation context

The source bundle does not report active exploitation, and the CVE is not listed as KEV. Exploitation requires local low-privileged ability to run or influence TensorFlow operations. The expected impact is process crash and availability loss.

Researcher notes

Evidence supports a signed-to-unsigned conversion flaw in boosted_trees_create_quantile_stream_resource. The provided sources identify patched versions and the fixing commit, but do not provide evidence of exploitation in the wild or broader product impact beyond TensorFlow.

Mitigation direction

  • Upgrade to TensorFlow 2.6.0 or patched supported releases 2.5.1, 2.4.3, or 2.3.4.
  • Prioritize shared ML services where untrusted users can run TensorFlow workloads.
  • Restrict access to affected TensorFlow execution environments until patched.
  • Review TensorFlow advisory GHSA-gf88-j2mg-cc82 for vendor guidance.

Validation and detection

  • Inventory TensorFlow versions in applications, notebooks, containers, and ML job images.
  • Flag versions >=2.5.0 <2.5.1, >=2.4.0 <2.4.3, and <2.3.4.
  • Check whether boosted trees TensorFlow operations are reachable in shared workloads.
  • Confirm deployed builds include commit 8a84f7a2b5a2b27ecf88d25bad9ac777cd2f7992 or later patched releases.
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-681: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-37661 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
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
5.5CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H1.83.6Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

5.5Medium
CVSS 3.1 vector shape for CVE-2021-37661Attack 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
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-681 · source CWE mapping

Incorrect Conversion between Numeric Types

Incorrect Conversion between Numeric Types represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.