CyberSecBulletin
CVE-2024-28757NVD status: Modified

SIMATIC S7-1500 CPU 1518-4 PN/DP MFP…: Improper Restriction of Recursive Entity References in DTDs

Published Updated By the CyberSecBulletin desk

CVE-2024-28757 is a high-severity improper restriction of recursive entity references in dtds vulnerability in SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) from Siemens, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version V3.1.5 as the first without the flaw, so updating SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 2.03% chance of exploitation within 30 days, higher than 81% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) to V3.1.5 or a later version.
  2. Update SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) to V3.1.5 or a later version.
  3. Update SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) to V3.1.5 or a later version.
  4. 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
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)V3.1.0 up to, but not including, V3.1.5; V3.1.7 and laterV3.1.5
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)V3.1.0 up to, but not including, V3.1.5; V3.1.7 and laterV3.1.5
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)V3.1.0 up to, but not including, V3.1.5; V3.1.7 and laterV3.1.5
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)V3.1.0 up to, but not including, V3.1.5; V3.1.7 and laterV3.1.5
SiemensSINEC NMSbefore V3.0V3.0
SiemensSIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)V3.1.0 up to, but not including, V3.1.5; V3.1.7 and laterV3.1.5
Libexpat ProjectLibexpatbefore 2.6.22.6.2
Fedora ProjectFedora38; 39; 40Not stated
NetAppActive Iq Unified ManagerNot specified in the recordNot stated
NetAppOncommand Workflow AutomationNot specified in the recordNot stated
NetAppOntap9Not stated
NetAppOntap Tools10Not stated
NetAppWindows Host UtilitiesNot specified in the recordNot stated
NetAppH300s FirmwareNot specified in the recordNot stated
NetAppH500s FirmwareNot specified in the recordNot stated
NetAppH700s FirmwareNot specified in the recordNot stated
NetAppH410s FirmwareNot specified in the recordNot stated
NetAppH410c FirmwareNot specified in the recordNot stated
NetAppH610c FirmwareNot specified in the recordNot stated
NetAppH610s FirmwareNot specified in the recordNot stated

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
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

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

Scoring systemScoreSeverityScored by
CVSS 3.17.5HighNVD
CVSS 3.17.5HighCISA (ADP)

Official description

libexpat through 2.6.1 allows an XML Entity Expansion attack when there is isolated use of external parsers (created via XML_ExternalEntityParserCreate).

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

The underlying weakness: Improper Restriction of Recursive Entity References in DTDs

The product uses XML documents and allows their structure to be defined with a Document Type Definition (DTD), but it does not properly control the number of recursive definitions of entities.

How developers prevent this class of flaw

  • If possible, prohibit the use of DTDs or use an XML parser that limits the expansion of recursive DTD entities.
  • Before parsing XML files with associated DTDs, scan for recursive entity declarations and do not continue parsing potentially explosive content.

More Improper Restriction of Recursive Entity References in DTDs vulnerabilities (CWE-776)

Timeline

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

References

Patches and release notes

Third-party and government advisories

Other references

Other vulnerabilities in SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)

All SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) vulnerabilities

Recent Improper Restriction of Recursive Entity References in DTDs vulnerabilities

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