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Response snapshot Nov 2, 2026, 02:36 UTC

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VulnerabilityCVE-2026-83594

Memory allocation with an excessive size value in Apache Wicket.

Memory allocation with an excessive size value in Apache Wicket. org.apache.wicket.markup.html.form.upload.resource.FileUploadToResourceField uploads files to a separately mounted resource rather than through a form, and is told the outcome afterwards over its own Ajax callback.

At a glance

Exploited
Not known
Severity
8.3 High (CVSS 4.0)
Chance of exploitation
Not estimated
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-83594 (opens a new tab)

What happened

Memory allocation with an excessive size value in Apache Wicket.

org.apache.wicket.markup.html.form.upload.resource.FileUploadToResourceField uploads files to a separately mounted resource rather than through a form, and is told the outcome afterwards over its own Ajax callback. That callback reads the request parameter filesInfo, a JSON array carrying a client file name, a size and a content type for each file, and turns it into the list of FileUploadToResourceField.

UploadInfo that onUploadSuccess() receives. Nothing binds that JSON to an upload the resource performed and nothing re-derives it from the stored files, so the number of entries and every value in them are whatever the request supplied.

The callback URL is rendered into the page, no prior upload is required, and both GET and POST reach it, so any client that can load the page can have the component report files that were never uploaded, without authenticating beyond whatever the page itself requires and without any user interaction.

Continue reading

UploadInfo#get(), which the class offers as the way to obtain the bytes of an upload, allocates a byte array from UploadInfo#getSize() before it opens the file. The array is therefore sized by the number the request supplied, and the allocation happens even for a file that was never stored.

One small request can cost the server close to two gigabytes of heap, and the request is trivially repeatable, so a few of them exhaust the heap for every request the Java virtual machine is serving. A size that the conversion to int turns negative instead throws NegativeArraySizeException, which the exception handler inside that method does not cover, so it escapes into the application.

An application is affected where it uses FileUploadToResourceField, which is not the ordinary upload path through FileUploadField and Form and has to be extended and mounted deliberately. The allocation additionally requires the application to call UploadInfo#get() rather than reading UploadInfo#getFile() itself.

Where the application denies the ENABLE action on the field through its authorization strategy, the callback is refused like any other listener. The 8.x line does not contain this component and is not affected.

This issue affects Apache Wicket: from 9.14.0 through 9.24.0, from 10.0.0 through 10.11.0. Users are recommended to upgrade to version 9.25.0 or 10.12.0, which fix the issue.

Scores and how they were measured

CVSS base severity

8.3

Version 4.0As of

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Sources

  1. Primary source

    NVD CVE-2026-83594 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  4. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, November 1). Memory allocation with an excessive size value in Apache Wicket. (CVE-2026-83594). https://kevwire.com/record/CVE-2026-83594

MLA

"Memory allocation with an excessive size value in Apache Wicket. (CVE-2026-83594)." KEVWire, 1 Nov. 2026, kevwire.com/record/CVE-2026-83594.

Chicago

KEVWire. "Memory allocation with an excessive size value in Apache Wicket. (CVE-2026-83594)." Last modified November 1, 2026. https://kevwire.com/record/CVE-2026-83594.

Evidence summary (plain text)

Memory allocation with an excessive size value in Apache Wicket. (Nov 1, 2026).
Memory allocation with an excessive size value in Apache Wicket.

org.apache.wicket.markup.html.form.upload.resource.FileUploadToResourceField uploads files to a separately mounted resource rather than through a form, and is told the outcome afterwards over its own Ajax callback. That callback reads the request parameter filesInfo, a JSON array carrying a client file name, a size and a content type for each file, and turns it into the list of FileUploadToResourceField.UploadInfo that onUploadSuccess() receives.
CVSS 8.3 (version 4.0; evidence as of Nov 1, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-83594).
Sources:
NVD CVE-2026-83594: https://nvd.nist.gov/vuln/detail/CVE-2026-83594
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-01T23:15:57.054Z&lastModEndDate=2026-11-02T00:50:55.984Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-01T22:40:59.243Z&lastModEndDate=2026-11-02T00:15:55.446Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-01T22:05:59.838Z&lastModEndDate=2026-11-01T23:40:56.426Z&resultsPerPage=500&startIndex=0
Record ID: CVE-2026-83594.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Nov 2, 2026, 00:50 UTC. Ingestion is not an independent editorial investigation.

NVD status: Received. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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