SVG sanitization bypass via case-sensitive MIME check
Published May 30, 2023 · Updated Jan 10, 2025
Improper input validation in Nextcloud Contacts allows remote authenticated users to bypass SVG sanitization via mixed-case MIME data. The Contact photo handler checks whether photoType starts with lowercase svg before calling sanitizeSVG, so mixed-case values skip sanitization. Authenticated contact editing reaches the code, but Avatar cannot render the resulting JavaScript blob, and Nextcloud reports no exploitable consequence.
Summary
What happened
Improper input validation in Nextcloud Contacts allows remote authenticated users to bypass SVG sanitization via mixed-case MIME data. The Contact photo handler checks whether photoType starts with lowercase svg before calling sanitizeSVG, so mixed-case values skip sanitization. Authenticated contact editing reaches the code, but Avatar cannot render the resulting JavaScript blob, and Nextcloud reports no exploitable consequence.
The record
- CVE
- CVE-2023-33182
- Published
- May 30, 2023
- Updated
- Jan 10, 2025
- Vendor
- Nextcloud GmbH
- Product
- Security Advisories
- Classifications
- CWE-20
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- May 30, 2023CVE publishedPublication date reported by the CVE source.
- Jan 10, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=>= 4.1.0, < 4.2.4
- Affected versionversion=>= 5.0.0, < 5.0.3
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What is affected?
Published CVSS scores
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Attacks
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Public exploit references
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Technologies
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Your stack
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