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CVE Record

CVE-2026-8657: Versions of the package jsondiffpatch before 0.7.6 are vulnerable to Prototype Pollution via the jsondiffpa...

Versions of the package jsondiffpatch before 0.7.6 are vulnerable to Prototype Pollution via the jsondiffpatch.patch() and jsondiffpatch/formatters/jsonpatch.patch() APIs. An attacker can perform prototype pollution by supplying crafted delta or JSON Patch documents, as attacker-controlled property names and path segments are used to traverse and modify objects without restricting access to special properties like __proto__ or constructor.prototype, allowing modification of Object.prototype.

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Applications using vulnerable jsondiffpatch versions may let untrusted patch data alter shared JavaScript object behavior. This can corrupt application logic, weaken security decisions, expose data, or disrupt service. Risk depends on whether attackers can submit delta or JSON Patch documents that the application processes.

Executive priority

Treat as a high-priority dependency update for externally reachable systems processing user-controlled patches. Confirm exposure promptly, upgrade affected deployments, and investigate unexpected object-property behavior. Systems without untrusted patch inputs can follow normal expedited patching after validation.

Technical view

jsondiffpatch versions before 0.7.6 insufficiently restrict special property names during object traversal. Crafted input supplied to jsondiffpatch.patch() or jsondiffpatch/formatters/jsonpatch.patch() can reach __proto__ or constructor.prototype and modify Object.prototype, causing prototype pollution across affected application objects.

Likely exposure

Exposure is most likely in internet-facing or multi-tenant services that process attacker-controlled delta or JSON Patch documents using affected APIs. Applications using the package only with trusted, internally generated patches have lower practical exposure. Both the npm package and its WebJars packaging should be inventoried.

Exploitation context

The supplied record reports network-accessible, low-complexity exploitation without privileges or user interaction and references a public technical demonstration. It does not identify confirmed attacks in the wild, and the CVE is not listed as KEV in the provided bundle.

Researcher notes

The vulnerable traversal occurs in both native delta application and JSON Patch application paths. The security boundary failure is unrestricted traversal through prototype-sensitive names. Impact is application-dependent; the bundle supports integrity and availability risk but does not establish a universal path to code execution.

Mitigation direction

  • Upgrade jsondiffpatch and affected WebJars dependencies to version 0.7.6 or later.
  • Prioritize services accepting untrusted delta or JSON Patch documents.
  • Temporarily reject untrusted patch documents where immediate upgrading is impossible.
  • Check vendor guidance and lockfiles for additional dependency-specific remediation details.

Validation and detection

  • Inventory direct and transitive jsondiffpatch and WebJars versions across deployed applications.
  • Identify every call to jsondiffpatch.patch() and jsonpatch.patch().
  • Trace whether external users can influence patch property names or path segments.
  • Confirm resolved production versions are 0.7.6 or later.
  • Run regression tests covering rejection of special prototype-related property paths.
Prepared
Confidence
high
Sources
6

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

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cve · low confidence lookup

CVE-2026-8657 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.8 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:P

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.

2CVSS vectors
3Timeline events
1ADP providers
9Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

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
8.8CVSS 4.0HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:P——snyk
8.2CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L/E:P3.94.2snyk

Vulnerability scoring details

Base CVSS 4.0 score

8.8High
CVSS 4.0 vector shape for CVE-2026-8657Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:P

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/ajsondiffpatch0Listed
n/aorg.webjars.npm:jsondiffpatch0Listed
Weakness

CWE details

CWE-1321

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

CWE-1321 · source CWE mapping

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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