CyberSecBulletin
CVE-2021-26085Exploited in the wildNVD status: Analyzed

Atlassian Confluence Server Pre-Authorization Arbitrary File Read

Published Updated By the CyberSecBulletin desk

CVE-2021-26085 is a medium-severity direct request vulnerability in Confluence Server from Atlassian, with a CVSS 3.1 base score of 5.3 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 7.4.10, 7.12.3 as the first without the flaw, so updating Confluence Server to one of those releases or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on March 28, 2022, which means attacks have been observed in the wild, including in ransomware campaigns.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Confluence Server to 7.4.10 or 7.12.3, whichever matches your release line, or a later version.
  2. Update Confluence Data Center to 7.4.10 or 7.12.3, whichever matches your release line, or a later version.
  3. CISA's required action: Apply updates per vendor instructions.
  4. Read the advisory on jira.atlassian.com for workarounds and exact fixed builds.
  5. 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
AtlassianConfluence Serverbefore 7.4.10; 7.5.0; before 7.12.37.4.10, 7.12.3
AtlassianConfluence Data Centerbefore 7.4.10; 7.5.0; before 7.12.37.4.10, 7.12.3

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
LowSome restricted data can be read.
Integrity
NoneNothing can be modified.
Availability
NoneAvailability is not affected.

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

Scoring systemScoreSeverityScored by
CVSS 3.15.3MediumNVD
CVSS 3.15.3MediumCISA (ADP)
CVSS 2.05.0MediumNVD

Official description

Affected versions of Atlassian Confluence Server allow remote attackers to view restricted resources via a Pre-Authorization Arbitrary File Read vulnerability in the /s/ endpoint. The affected versions are before version 7.4.10, and from version 7.5.0 before 7.12.3.

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

The underlying weakness: Direct Request

The web application does not adequately enforce appropriate authorization on all restricted URLs, scripts, or files.

How developers prevent this class of flaw

  • Apply appropriate access control authorizations for each access to all restricted URLs, scripts or files.
  • Consider using MVC based frameworks such as Struts.

More Direct Request vulnerabilities (CWE-425)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. Deadline for US federal agencies to remediate, set by CISA.
  4. CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: partial).
  5. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Technical write-ups (may include proof of concept)

Other vulnerabilities in Confluence Server

All Confluence Server vulnerabilities

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