CyberSecBulletin
CVE-2023-42796NVD status: Modified

CP-8031 MASTER MODULE: Improper Limitation of a Pathname to a Restricted Directory

Published Updated By the CyberSecBulletin desk

CVE-2023-42796 is a high-severity improper limitation of a pathname to a restricted directory vulnerability in CP-8031 MASTER MODULE from Siemens, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected CP-8031 MASTER MODULE versions: All versions < CPCI85 V05.11. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.97% chance of exploitation within 30 days, higher than 63% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Cp-8050 Firmware to 05.11 or a later version.
  2. Update Cp-8031 Firmware to 05.11 or a later version.
  3. Read the advisory on cert-portal.siemens.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
SiemensCP-8031 MASTER MODULEAll versions < CPCI85 V05.11Not stated
SiemensCP-8050 MASTER MODULEAll versions < CPCI85 V05.11Not stated
SiemensCp-8050 Firmwarebefore 05.1105.11
SiemensCp-8031 Firmwarebefore 05.1105.11

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
LowA basic user account is enough.
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
HighThe component can be taken down completely.

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

Scoring systemScoreSeverityScored by
CVSS 3.17.5HighCNA (siemens.com)
CVSS 3.18.8HighNVD

Official description

A vulnerability has been identified in CP-8031 MASTER MODULE (All versions < CPCI85 V05.11), CP-8050 MASTER MODULE (All versions < CPCI85 V05.11). The web server of affected devices fails to properly sanitize user input for the /sicweb-ajax/tmproot/ endpoint. This could allow an authenticated remote attacker to traverse directories on the system and download arbitrary files. By exploring active session IDs, the vulnerability could potentially be leveraged to escalate privileges to the administrator role.

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

The underlying weakness: Improper Limitation of a Pathname to a Restricted Directory

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

How developers prevent this class of flaw

  • For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
  • Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.

More Improper Limitation of a Pathname to a Restricted Directory vulnerabilities (CWE-22)

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

Other vulnerabilities in CP-8031 MASTER MODULE

All CP-8031 MASTER MODULE vulnerabilities

Recent Improper Limitation of a Pathname to a Restricted Directory vulnerabilities

Spotted an error? Tell us.