NewsCompaniesFlawsGuides
Get the app

CVE-2023-41763

From Exploited flaws, HARD’s guide to the flaws being used in attacks · Checked
This article is about a flaw in Microsoft Skype for Business. For every flaw being used in attacks, see Exploited flaws; for Microsoft’s, see Microsoft flaws being used in attacks.

CVE-2023-41763 is a security flaw in Microsoft Skype for Business. Someone who already has a foothold can use Microsoft Skype for Business to take full control of the machine. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 10 Oct 2023.[1]

Microsoft Skype for Business is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Fixed in version 6.0.9319.869 and 7.0.246.530.

Description

CISA calls it a privilege escalation in Microsoft Skype for Business. In its words: “Microsoft Skype for Business contains an unspecified vulnerability that allows for privilege escalation.”[1]

The underlying weakness is server-side request forgery (CWE-918), in MITRE’s list of common software weaknesses.[2]

It scores 5.3 out of 10 on the Common Vulnerability Scoring System, which rates it medium, scored by the organisation that published the CVE using CVSS 3.1.[2]

Affected versions

NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]

ProductFixed in
Skype for Business Server 2015 CU136.0.9319.869
Skype for Business Server 2019 CU77.0.246.530

Most families won’t have Microsoft Skype for Business; it’s for whoever looks after IT at work.

Exploitation

CISA added it to its catalog of known exploited vulnerabilities on 10 Oct 2023, within a day of it being made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 31 Oct 2023 to fix it.[1]

FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 91%. That’s in the top 1% of the flaws it scores.[4]

CISA assesses it as automatable: attackers can run it against many targets at once.

CISA doesn’t say who was attacked, or how.

Fix

Microsoft has published a fix or advice.[3] CISA’s required action: “Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.”[1]

  1. Check whether you use it.Microsoft Skype for Business is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
  2. Send this page to your IT person.Ask them to confirm it’s fixed (fixed in version 6.0.9319.869 and 7.0.246.530), or not in use. CISA gave US government agencies until 31 Oct 2023 to fix it.
  3. If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.

You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.

Timeline

DateEvent
The flaw is made public in the National Vulnerability Database, with a severity score of 5.3.[2]
CISA adds it to its catalog of flaws known to be used in attacks.[1]
CISA’s deadline for US government agencies to fix it.[1]
FIRST puts the odds of it being used in attacks in the next 30 days at 91%.[4]

See also

Other Microsoft flaws

  • CVE-2026-96951, Microsoft Windows: command injection ·
  • CVE-2026-65660, Microsoft SharePoint: code injection ·
  • CVE-2026-85880, Microsoft Windows: heap-based buffer overflow ·
  • CVE-2026-81963, Microsoft Windows: link following ·
  • CVE-2019-1068, Microsoft SQL Server: remote code execution ·

Other server-side request forgery flaws

  • CVE-2026-96655, Plex Media Server: server-side request forgery (SSRF) ·
  • CVE-2026-96652, Plex Media Server: server-side request forgery (SSRF) ·
  • CVE-2026-83548, SonicWall SMA1000 Appliances: server-side request forgery ·
  • CVE-2026-64849, MLflow: server-side request forgery ·
  • CVE-2026-15409, SonicWall SMA1000 Appliances: server-side request forgery ·

Added the same day

  • CVE-2023-44487, IETF HTTP/2: rapid reset attack ·
  • CVE-2023-36563, Microsoft WordPad: information disclosure ·
  • CVE-2023-21608, Adobe Acrobat and Reader: use-after-free ·
  • CVE-2023-20109, Cisco IOS and IOS XE: group encrypted transport VPN out-of-bounds write ·

Every Microsoft flaw on CISA’s list · Everything added in October 2023

References

  1. ^ Cybersecurity and Infrastructure Security Agency. “Microsoft Skype for Business Privilege Escalation Vulnerability”. Known Exploited Vulnerabilities Catalog, added 10 Oct 2023.
  2. ^ National Institute of Standards and Technology. “CVE-2023-41763 Detail”. National Vulnerability Database, published 10 Oct 2023.
  3. ^ Microsoft. Advisories and fixes: msrc.microsoft.com, msrc.microsoft.com.
  4. ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.905, percentile 99.8, 31 Oct 2026.
  5. CVE Program. “CVE-2023-41763”. The official CVE record.

This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.