CVE-2023-28999 | Nextcloud: Lack of authenticity of metadata keys allows a malicious server to gain access to E2EE folders

Exp

Nextcloud is an open-source productivity platform. In Nextcloud Desktop client 3.0.0 until 3.8.0, Nextcloud Android app 3.13.0 until 3.25.0, and Nextcloud iOS app 3.0.5 until 4.8.0, a malicious server administrator can gain full access to an end-to-end encrypted folder. They can decrypt files, recover the folder structure and add new files.​ This issue is fixed in Nextcloud Desktop 3.8.0, Nextcloud Android 3.25.0, and Nextcloud iOS 4.8.0. No known workarounds are available.

Published: 2023-04-04 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-28999 is rated Exploit Available (59.4/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.68%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2023-28999

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2023-28999

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.45% 0.68% +0.23%
2 2026-06-12 1.28% 0.45% -0.84%
3 2026-05-03 — 1.28% —

Full EPSS history (45 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-28999

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.9 3.1 MEDIUM
CVSS:3.1/AV:P/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:L Click to expand
Attack vector (AV:P)
Hands-on access—USB, keyboard, opening the case—not something you do purely over the wire.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 0.4 6.0 [email protected]
6.4 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 0.9 5.5 [email protected]

Weakness enumeration for CVE-2023-28999

OS Trackers for CVE-2023-28999

vendor priority summary link
alpine medium CVE-2023-28999: 1 source package rows (nextcloud-client); 6 state rows across 6 repos (3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 6, open 0. https://security.alpinelinux.org/vuln/CVE-2023-28999
debian not yet assigned CVE-2023-28999 not yet assigned priority: Debian including 1 source packages (nextcloud-desktop), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 3, open 2. https://security-tracker.debian.org/tracker/CVE-2023-28999
suse medium — https://www.suse.com/security/cve/CVE-2023-28999/
ubuntu medium CVE-2023-28999 medium priority: Ubuntu including 1 source packages (nextcloud-desktop), 13 status rows across 13 suites (bionic, focal, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): ignored 7, needs-triage 5, DNE 1. https://ubuntu.com/security/CVE-2023-28999

Affected software / configurations for CVE-2023-28999

Vendor Product Version Raw CPE
nextcloud desktop >= 3.0.0, < 3.8.0 cpe:2.3:a:nextcloud:desktop:*:*:*:*:*:*:*:*
nextcloud nextcloud >= 3.0.5, < 4.8.0 cpe:2.3:a:nextcloud:nextcloud:*:*:*:*:iphone_os:*:*:*
nextcloud nextcloud >= 3.13.0, < 3.25.0 cpe:2.3:a:nextcloud:nextcloud:*:*:*:*:android:*:*:*

References for CVE-2023-28999

cvelogic Threat Intelligence