A too small set of random characters being used for encryption in Nextcloud Server 18.0.4 allowed decryption in shorter time than intended.

published 2020-10-30 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-29057

cvss: 2.2; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 30%
public exploits: 0; none known

Patch / fix

fixed in 1

nextcloud nextcloud_server 17.0.7, 18.0.5

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-2020-8173 updated 2025-11-21 cvss 2.2

nextcloud: random characters allowed decryption in shorter time than intended

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

0.37% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

hackerone.com https://hackerone.com/reports/852841 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	2.2	CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:N
NVD	2.0	3.5	AV:N/AC:M/Au:S/C:P/I:N/A:N

Affected products

n/a Nextcloud Server

Classification

Weakness

CWE-310 Cryptographic Issues
CWE-311 Missing Encryption of Sensitive Data

References

hackerone.com /reports/852841
exploit, third-party-advisory
nextcloud.com /security/advisory/?id=NC-SA-2020-023
broken-link, vendor-advisory

Sources

CVE List CVE-2020-8173
NVD CVE-2020-8173

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