CyberSecBulletin
CVE-2024-43451Exploited in the wildNVD status: Analyzed

Microsoft Windows NTLMv2 Hash Disclosure Spoofing

Published Updated By the CyberSecBulletin desk

CVE-2024-43451 is a medium-severity external control of file name or path vulnerability in Windows Server 2025 from Microsoft, with a CVSS 3.1 base score of 6.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists version 10.0.26100.2314 as the first without the flaw, so updating Windows Server 2025 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on November 12, 2024, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Windows Server 2025 to 10.0.26100.2314 or a later version.
  2. Update Windows Server 2025 (Server Core installation) to 10.0.26100.2314 or a later version.
  3. Update Windows 10 Version 1809 to 10.0.17763.6532 or a later version.
  4. CISA's required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
  5. Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
  6. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
  7. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
MicrosoftWindows Server 202510.0.26100.0 up to, but not including, 10.0.26100.231410.0.26100.2314
MicrosoftWindows Server 2025 (Server Core installation)10.0.26100.0 up to, but not including, 10.0.26100.231410.0.26100.2314
MicrosoftWindows 10 Version 180910.0.17763.0 up to, but not including, 10.0.17763.653210.0.17763.6532
MicrosoftWindows Server 201910.0.17763.0 up to, but not including, 10.0.17763.653210.0.17763.6532
MicrosoftWindows Server 2019 (Server Core installation)10.0.17763.0 up to, but not including, 10.0.17763.653210.0.17763.6532
MicrosoftWindows Server 202210.0.20348.0 up to, but not including, 10.0.20348.284910.0.20348.2849
MicrosoftWindows 10 Version 21H210.0.19043.0 up to, but not including, 10.0.19044.513110.0.19044.5131
MicrosoftWindows 11 version 22H210.0.22621.0 up to, but not including, 10.0.22621.446010.0.22621.4460
MicrosoftWindows 10 Version 22H210.0.19045.0 up to, but not including, 10.0.19045.513110.0.19045.5131
MicrosoftWindows 11 version 22H310.0.22631.0 up to, but not including, 10.0.22631.446010.0.22631.4460
MicrosoftWindows 11 Version 23H210.0.22631.0 up to, but not including, 10.0.22631.446010.0.22631.4460
MicrosoftWindows Server 2022, 23H2 Edition (Server Core installation)10.0.25398.0 up to, but not including, 10.0.25398.125110.0.25398.1251
MicrosoftWindows 11 Version 24H210.0.26100.0 up to, but not including, 10.0.26100.231410.0.26100.2314
MicrosoftWindows 10 Version 150710.0.10240.0 up to, but not including, 10.0.10240.2082610.0.10240.20826
MicrosoftWindows 10 Version 160710.0.14393.0 up to, but not including, 10.0.14393.751510.0.14393.7515
MicrosoftWindows Server 201610.0.14393.0 up to, but not including, 10.0.14393.751510.0.14393.7515
MicrosoftWindows Server 2016 (Server Core installation)10.0.14393.0 up to, but not including, 10.0.14393.751510.0.14393.7515
MicrosoftWindows Server 2008 Service Pack 26.0.6003.0 up to, but not including, 6.0.6003.229666.0.6003.22966
MicrosoftWindows Server 2008 Service Pack 2 (Server Core installation)6.0.6003.0 up to, but not including, 6.0.6003.229666.0.6003.22966
MicrosoftWindows Server 2008 R2 Service Pack 16.1.7601.0 up to, but not including, 6.1.7601.274156.1.7601.27415
MicrosoftWindows Server 2008 R2 Service Pack 1 (Server Core installation)6.1.7601.0 up to, but not including, 6.1.7601.274156.1.7601.27415
MicrosoftWindows Server 2012 R26.3.9600.0 up to, but not including, 6.3.9600.222676.3.9600.22267
MicrosoftWindows Server 2012 R2 (Server Core installation)6.3.9600.0 up to, but not including, 6.3.9600.222676.3.9600.22267
MicrosoftWindows 10 1507before 10.0.10240.2082610.0.10240.20826
MicrosoftWindows 10 1607before 10.0.14393.751510.0.14393.7515

Version data comes from the organisation that assigned the CVE; 9 further products are omitted here. 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
RequiredA user must take an action such as opening a file or link.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
NoneNothing can be modified.
Availability
NoneAvailability is not affected.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N. Scored by CNA (microsoft.com).

Official description

NTLM Hash Disclosure Spoofing Vulnerability

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

The underlying weakness: External Control of File Name or Path

The product allows user input to control or influence paths or file names that are used in filesystem operations.

How developers prevent this class of flaw

  • When the set of filenames is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames, and reject all other inputs. For example, ID 1 could map to inbox.txt and ID 2 could map to profile.txt. Features such as the ESAPI AccessReferenceMap provide this capability.
  • Run your code in a jail or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict all access to files within a particular directory. Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of your application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
  • 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.

More External Control of File Name or Path vulnerabilities (CWE-73)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: partial).
  4. Deadline for US federal agencies to remediate, set by CISA.
  5. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Recent External Control of File Name or Path vulnerabilities

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