CVE-2023-29357
CVE-2023-29357 is a security flaw in Microsoft SharePoint Server, Microsoft’s software for company intranets and shared documents. Attackers can use Microsoft SharePoint Server to take full control of the machine from anywhere, without logging in. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 10 Jan 2024, and says ransomware gangs have used it.[1]
Microsoft SharePoint Server 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 16.0.10399.20005 of Microsoft SharePoint Server 2019.
Description
CISA calls it a privilege escalation in Microsoft SharePoint Server. In its words: “Microsoft SharePoint Server contains an unspecified vulnerability that allows an unauthenticated attacker, who has gained access to spoofed JWT authentication tokens, to use them for executing a network attack. This attack bypasses authentication, enabling the attacker to gain administrator privileges.”[1]
The underlying weakness is CWE-303, in MITRE’s list of common software weaknesses.[2]
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record lists one fixed version: everything before it is affected.[2]
| Product | Fixed in |
|---|---|
| Microsoft SharePoint Server 2019 | 16.0.10399.20005 |
Most families won’t have Microsoft SharePoint Server; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 10 Jan 2024, 210 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 31 Jan 2024 to fix it.[1] CISA says ransomware gangs have used it.
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 over 99%. 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]
- Check whether you use it.Microsoft SharePoint Server 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.
- Send this page to your IT person.Ask them to confirm it’s fixed (fixed in version 16.0.10399.20005 of Microsoft SharePoint Server 2019), or not in use. CISA gave US government agencies until 31 Jan 2024 to fix it.
- 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
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks, noting that ransomware gangs have used it.[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 over 99%.[4] |
See also
Other Microsoft SharePoint Server flaws
- CVE-2026-56164: missing authentication for critical function ·
- CVE-2026-45659: deserialization of untrusted data ·
- CVE-2026-32201: improper input validation ·
- CVE-2023-24955: code injection ·
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 ·
Added the same day
- CVE-2024-21887, Ivanti Connect Secure and Policy Secure: command injection ·
- CVE-2023-46805, Ivanti Connect Secure and Policy Secure: authentication bypass ·
Every Microsoft flaw on CISA’s list · Everything added in January 2024
References
- ^ Cybersecurity and Infrastructure Security Agency. “Microsoft SharePoint Server Privilege Escalation Vulnerability”. Known Exploited Vulnerabilities Catalog, added 10 Jan 2024.
- ^ National Institute of Standards and Technology. “CVE-2023-29357 Detail”. National Vulnerability Database, published 14 Jun 2023.
- ^ Microsoft. Advisories and fixes: msrc.microsoft.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 1.000, percentile 100.0, 31 Oct 2026.
- CVE Program. “CVE-2023-29357”. 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.