Microsoft has been forced to pull an update it issued as part of its August Patch Tuesday after it was found that the patch in question, meant to fix a spoofing vulnerability in Microsoft Exchange Server, would not install properly on non-English systems.

The company issued the patch, assigned CVE-2023-38181, on 8 August [Tuesday], describing it as follows: "An attacker who successfully exploited this vulnerability could access a user's Net-NTLMv2 hash which could be used as a basis of an NTLM Relay attack against another service to authenticate as the user."

In the update, issued on 9 August, the company said: "...an issue has been discovered with the non-English August updates of Exchange Server and you should postpone installing these updates.

"The script protecting customers from the vulnerability documented by CVE-2023-21709 can be run to protect against the vulnerability without installing the August updates. Microsoft recommends running the script."

The CVE-2023-21709 was assigned to an elevation of privilege flaw that had a CVSSv3 score of 9.8, but Microsoft rated it as an important flaw, not critical.

"We are aware of Setup issues on non-English servers and have temporarily removed August SU from Windows / Microsoft update," Microsoft said.

"If you are using a non-English language server, we recommend you wait with deployment of August SU until we provide more information."

Commenting on the incident, experienced British security guru Kevin Beaumont said: "Microsoft should really take their staff off trying to find exploits in other vendor's products and put their staff on their own products.

"The customer experience here is basically being shot at constantly by the same person with the same gun while MS are running around with their wangs out going 'we're the experts!!'

"(This vuln allows PowerShell remoting, btw (not just spoofing) which is really powerful... and the patch got pulled as it breaks non-English Exchange servers)."

Beaumont was referring to the fact that Microsoft often issues advisories about security issues with other companies' software, witrhout bothering to keep its own house in order.

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