CyberSecBulletin
CVE-2023-35172NVD status: Modified

security-advisories: Improper Restriction of Excessive Authentication Attempts

Published Updated By the CyberSecBulletin desk

CVE-2023-35172 is a critical-severity improper restriction of excessive authentication attempts vulnerability in security-advisories from Nextcloud, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected security-advisories versions: Nextcloud Server >= 25.0.0, < 25.0.7; Nextcloud Server >= 26.0.0, < 26.0.2; Nextcloud Enterprise Server >= 25.0.0, < 25.0.7, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.92% chance of exploitation within 30 days, higher than 61% of scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Nextcloud Server to 21.0.9.12 or 22.2.10.12 or 23.0.12.7 or 24.0.12.2, whichever matches your release line, or a later version.
  2. Read the advisory on github.com for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Nextcloudsecurity-advisoriesNextcloud Server >= 25.0.0, < 25.0.7; Nextcloud Server >= 26.0.0, < 26.0.2; Nextcloud Enterprise Server >= 25.0.0, < 25.0.7; Nextcloud Enterprise Server >= 26.0.0, < 26.0.2; Nextcloud Enterprise Server >= 21.0.0, < 21.0.9.12; Nextcloud Enterprise Server >= 22.0.0, < 22.2.10.12; Nextcloud Enterprise Server >= 23.0.0, < 23.0.12.7; Nextcloud Enterprise Server >= 24.0.0, < 24.0.12.2Not stated
NextcloudNextcloud Server21.0.0 up to, but not including, 21.0.9.12; 22.0.0 up to, but not including, 22.2.10.12; 23.0.0 up to, but not including, 23.0.12.7; 24.0.0 up to, but not including, 24.0.12.2; 25.0.0 up to, but not including, 25.0.7; 26.0.0 up to, but not including, 26.0.221.0.9.12, 22.2.10.12, 23.0.12.7, 24.0.12.2, 25.0.7, 26.0.2

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
NoneAvailability is not affected.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.18.7HighCNA (github.com)
CVSS 3.19.1CriticalNVD

Official description

NextCloud Server and NextCloud Enterprise Server provide file storage for Nextcloud, a self-hosted productivity platform. In NextCloud Server versions 25.0.0 until 25.0.7 and 26.0.0 until 26.0.2 and Nextcloud Enterprise Server versions 21.0.0 until 21.0.9.12, 22.0.0 until 22.2.10.12, 23.0.0 until 23.0.12.7, 24.0.0 until 24.0.12.2, 25.0.0 until 25.0.7, and 26.0.0 until 26.0.2, an attacker can bruteforce the password reset links. Nextcloud Server n 25.0.7 and 26.0.2 and Nextcloud Enterprise Server 21.0.9.12, 22.2.10.12, 23.0.12.7, 24.0.12.2, 25.0.7, and 26.0.2 contain a patch for this issue. No known workarounds are available.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Restriction of Excessive Authentication Attempts

The product does not implement sufficient measures to prevent multiple failed authentication attempts within a short time frame.

How developers prevent this class of flaw

  • Common protection mechanisms include: Disconnecting the user after a small number of failed attempts Implementing a timeout Locking out a targeted account Requiring a computational task on the user's part.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Consider using libraries with authentication capabilities such as OpenSSL or the ESAPI Authenticator.

More Improper Restriction of Excessive Authentication Attempts vulnerabilities (CWE-307)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Patches and release notes

Other references

Other vulnerabilities in security-advisories

All security-advisories vulnerabilities

Recent Improper Restriction of Excessive Authentication Attempts vulnerabilities

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