CVE-2023-28997

Encrypted file disclosure and modification via IV reuse

Published Apr 4, 2023 · Updated Nov 3, 2025

Cryptographic failure in Nextcloud Desktop Client 3.0.0 through 3.6.4 allows attackers to read and alter end-to-end encrypted files. PropagateUploadEncrypted::slotFolderEncryptedMetadataReceived generated a random initialization vector only for new metadata, so later uploads of an existing encrypted file reused the stored vector. Exploitation requires administrative control of the connected Nextcloud server and a client reupload of an existing encrypted file; file confidentiality and integrity are affected, but service availability is not.

CVSS severity6.7
Medium
EPSS probability1.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cryptographic failure in Nextcloud Desktop Client 3.0.0 through 3.6.4 allows attackers to read and alter end-to-end encrypted files. PropagateUploadEncrypted::slotFolderEncryptedMetadataReceived generated a random initialization vector only for new metadata, so later uploads of an existing encrypted file reused the stored vector. Exploitation requires administrative control of the connected Nextcloud server and a client reupload of an existing encrypted file; file confidentiality and integrity are affected, but service availability is not.

The record

CVE
CVE-2023-28997
Published
Apr 4, 2023
Updated
Nov 3, 2025
Vendor
Nextcloud GmbH
Product
Security Advisories
Classifications
CWE-323
Attack vector
Unavailable
Privileges
admin

Timeline

How it unfolded

  1. Apr 4, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 3.0.0, < 3.6.5

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesadmin

What is affected?

Nextcloud GmbH · Security Advisoriesversion=>= 3.0.0, < 3.6.5

Published CVSS scores

6.7GitHub Security AdvisoryCVSS:3.1/AV:P/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:N
6.5NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-323Reusing a Nonce, Key Pair in Encryption

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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