A wrong generation of the passphrase for the encrypted block in Nextcloud Server 19.0.1 allowed an attacker to overwrite blocks in a file.

published 2020-11-09 5 y ago modified 2026-06-17 4 mo ago also EUVD-2020-29034

cvss: 5.3; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.7%; EPSS 0.7% chance of exploitation in 30 days, percentile 54%
public exploits: 0; none known

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-8133 updated 2025-11-21 cvss 5.3

nextcloud: Wrong generation of the passphrase for the encrypted block

Red Hat All currently supported Red Hat products
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.73% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

hackerone.com https://hackerone.com/reports/661051 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:P/A:N

Affected products

n/a Nextcloud Server

Classification

Weakness

CWE-657 Violation of Secure Design Principles
CWE-347 Improper Verification of Cryptographic Signature

References

hackerone.com /reports/661051
exploit, third-party-advisory
hackerone.com /reports/661051%2C
nextcloud.com /security/advisory/?id=NC-SA-2020-038
broken-link

Sources

CVE List CVE-2020-8133
NVD CVE-2020-8133

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary