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CVE Record

CVE-2026-42570: Svelte devalue: DoS via sparse array deserialization

Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. From version 5.6.3 to before version 5.8.1, devalue.parse could, due to quirks in some JavaScript engines, be convinced to allocate much more memory than was needed when deserializing sparse arrays, leading to excessive memory consumption. This issue has been patched in version 5.8.1.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This vulnerability can let an attacker make an affected application consume excessive memory while parsing certain serialized array data. The main business impact is service disruption, not data theft or tampering. It affects Svelte devalue versions 5.6.3 through 5.8.0 and is fixed in 5.8.1.

Executive priority

Treat this as a high-priority availability issue for exposed services, especially production systems that parse untrusted data. It does not indicate confidentiality or integrity compromise from the supplied sources, but denial of service can still cause customer-facing outages.

Technical view

devalue.parse can over-allocate memory when deserializing sparse arrays because of JavaScript engine behavior. The CVSS 3.1 score is 7.5 with network attack vector, low complexity, no privileges, no user interaction, and high availability impact only. The weakness is CWE-770.

Likely exposure

Exposure is most likely in JavaScript applications that directly or transitively use devalue 5.6.3 through 5.8.0 and parse untrusted serialized data. Server-side parsing paths are higher concern because memory exhaustion can affect availability for other users.

Exploitation context

The source bundle does not show known active exploitation, and KEV is false. Exploitation evidence is limited to the public vulnerability description and patch references. The risk is practical denial of service where attacker-controlled input reaches devalue.parse.

Researcher notes

The public record identifies the vulnerable range and fixed version, but does not provide active exploitation evidence. Focus validation on dependency reachability and whether attacker-controlled data reaches devalue.parse. Avoid developing attack payloads; use the advisory and patch to understand the allocation flaw.

Mitigation direction

  • Upgrade devalue to version 5.8.1 or later.
  • Refresh dependency lockfiles and redeploy affected applications.
  • Prioritize internet-facing services that parse client-supplied serialized data.
  • Reject or strictly limit untrusted serialized input until patched.
  • Follow vendor advisories for packaged or downstream copies.

Validation and detection

  • Inventory direct and transitive dependencies for devalue versions 5.6.3 through 5.8.0.
  • Identify code paths where devalue.parse handles user-controlled or third-party data.
  • Confirm deployed artifacts resolve devalue to 5.8.1 or later.
  • Review application monitoring for memory exhaustion or abnormal process restarts.
  • Check Red Hat advisories if using affected downstream packages.
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

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.

cwe · low confidence lookup

CWE-770: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-42570 mapping review

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

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/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.

2CVSS vectors
5Timeline events
2ADP providers
8Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: 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
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6GitHub_M
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-42570Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

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. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

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

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPdevalue: devalue: Excessive memory consumption via deserialization of sparse arrays
other:Red Hat severity ratingcvssV3_1
  • 2026-06-09T17:01:16.012Z: Reported to Red Hat.
  • 2026-06-09T16:12:26.377Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
sveltejsdevalue>= 5.6.3, < 5.8.1Listed
Weakness

CWE details

CWE-770

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

CWE-770 · source CWE mapping

Allocation of Resources Without Limits or Throttling

Allocation of Resources Without Limits or Throttling represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs