CVE-2026-9053
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedMothra would respect a default value given by a website for HTML file upload forms. An attacker could craft a website with a malicious default file path, and then conceal this form element.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceMothra browser incorrectly honors default values specified by websites for HTML file upload input fields. An attacker can pre-populate a file upload form with a path to a sensitive local file (e.g., /etc/passwd, user documents) and then hide the element using CSS, tricking users into unknowingly uploading arbitrary files from their system when they submit the form.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- Authentication
- None
- User interaction
- A
- Scope
- X
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N/E:P/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:N/R:A/V:X/RE:L/U:Amber
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Mothra browser engine versionRun 'about:version' or check the browser/application metadata to find the installed Mothra engine version numberAffected if The installed version falls within any affected version range (compare to vendor advisories)
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Verify file input default value behaviorCreate a test HTML file with an input element: <input type='file' value='/etc/passwd'> and load it in Mothra; inspect the file picker dialog that appearsAffected if The file picker dialog pre-populates with the attacker-supplied path (/etc/passwd) instead of a neutral default
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Check browser configuration for file path handlingInspect browser configuration files or settings related to file upload form behavior; look for options controlling default file path handlingAffected if Configuration allows or does not block website-supplied default values for file inputs
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Test with sensitive file path patternsLoad a webpage containing <input type='file' value='~/.ssh/id_rsa'> or similar paths to sensitive files; observe whether these paths are reflected in the upload interfaceAffected if The sensitive path appears pre-filled in the file selection dialog
A user is affected if the Mothra engine version accepts and uses website-supplied default value attributes on file input elements, causing pre-populated paths to sensitive files to appear in the upload dialog.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataConfigure Mothra to ignore website-specified default values for file upload input fields, requiring users to explicitly select files. This aligns with security best practices where file upload operations should always be user-initiated.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,888.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-9053 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-9053 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data