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CVE Record

CVE-2021-35121: An array index is improperly used to lock and unlock a mutex which can lead to a Use After Free condition I...

An array index is improperly used to lock and unlock a mutex which can lead to a Use After Free condition In the Synx driver in Snapdragon Compute, Snapdragon Connectivity, Snapdragon Industrial IOT, Snapdragon Mobile

MediumCVSS 6.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-35121 is a Qualcomm Snapdragon driver flaw that can cause memory to be used after it has been freed. The source bundle rates it medium severity, but successful exploitation could affect confidentiality, integrity, and availability. It requires local access and high privileges, which reduces typical business urgency.

Executive priority

Treat as a moderate firmware hygiene issue. Prioritize assets where affected Snapdragon hardware is used in managed mobile, IoT, or embedded environments, especially where devices can be locally accessed or already run privileged third-party code.

Technical view

In Qualcomm's Synx driver, an array index is improperly used when locking and unlocking a mutex, creating a use-after-free condition. The CVSS 3.1 score is 6.7 with local attack vector, low complexity, high privileges required, no user interaction, unchanged scope, and high C/I/A impact.

Likely exposure

Exposure is most likely in devices or embedded products using the listed Snapdragon Compute, Connectivity, Industrial IoT, or Mobile platforms. Network-only exposure is not indicated by the CVSS vector. Confirm exposure through device chipset, firmware, and OEM security bulletin mapping.

Exploitation context

The provided sources do not show CISA KEV listing or active exploitation evidence. Exploitation requires local access and high privileges, so this is more relevant to compromised, rooted, or locally controlled devices than remote unauthenticated attack scenarios.

Researcher notes

The public bundle identifies the bug class and affected Qualcomm platforms but does not provide exploit details, code paths, or a specific patched version. Avoid assuming downstream OEM coverage without checking each product's firmware advisory.

Mitigation direction

  • Check Qualcomm's June 2022 bulletin and OEM firmware guidance for affected platforms.
  • Prioritize firmware updates for managed devices using listed Snapdragon chipsets.
  • Track mobile, IoT, and embedded vendor advisories for downstream patch availability.
  • Restrict high-privilege local access on affected devices where operationally possible.

Validation and detection

  • Inventory devices and modules using the listed Qualcomm Snapdragon platforms.
  • Map device firmware levels against Qualcomm and OEM June 2022 security guidance.
  • Confirm whether the Synx driver is present in the deployed firmware image.
  • Review vulnerability scanners or SBOM data for CVE-2021-35121 coverage.
Prepared
Confidence
medium
Sources
3

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

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CVE-2021-35121 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
6.7 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:H/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
2Source 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
6.7CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H0.85.9Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

6.7Medium
CVSS 3.1 vector shape for CVE-2021-35121Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:H/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

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Qualcomm, Inc.Snapdragon Compute, Snapdragon Connectivity, Snapdragon Industrial IOT, Snapdragon MobileAPQ8053, MSM8953, QCA6390, QCA6391, QCA6426, QCA6436, QCM2290, QCM4290, QCS2290, QCS4290, QRB5165, QRB5165M, QRB5165N, SD460, SD662, SD680, SD690 5G, SD750G, SD765, SD765G, SD768G, SD865 5G, SD870, SDX55M, SDXR2 5G, SM7250P, WCD9326, WCD9370, WCD9375, WCD9380, WCD9385, WCN3615, WCN3680B, WCN3910, WCN3950, WCN3988, WCN3991, WCN3998, WCN6850, WCN6851, WSA8810, WSA8815, WSA8830, WSA8835Listed
Weakness

CWE details

No CWE listed

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