Read-state and IP disclosure via relative image URLs
Published Oct 25, 2021 · Updated Aug 4, 2024
Information disclosure in Nextcloud Mail before 1.10.4 allows remote authenticated users to expose read state and IP via crafted email. The privacy filter treats URLs without a scheme as safe because parsed relative URLs have an empty scheme, allowing an external image reference to render. Exploitation requires an authenticated mailbox user to send crafted HTML email and the recipient to open it; the consequence is limited to read-state and IP disclosure.
Summary
What happened
Information disclosure in Nextcloud Mail before 1.10.4 allows remote authenticated users to expose read state and IP via crafted email. The privacy filter treats URLs without a scheme as safe because parsed relative URLs have an empty scheme, allowing an external image reference to render. Exploitation requires an authenticated mailbox user to send crafted HTML email and the recipient to open it; the consequence is limited to read-state and IP disclosure.
The record
- CVE
- CVE-2021-39220
- Published
- Oct 25, 2021
- Updated
- Aug 4, 2024
- Vendor
- Nextcloud GmbH
- Product
- Nextcloud Security Advisories
- Classifications
- CWE-200, CWE-20
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Oct 25, 2021CVE publishedPublication date reported by the CVE source.
- Aug 4, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 1.10.4, < 1.11.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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