PT-2026-58045 · Microsoft · Sharepoint Server

CVE-2026-55040 · Published 2026-07-14 · Updated 2026-08-12

Positive Technologies (AI Summary)

CVSS v2.0

9.4

Critical

Base vector

AV:N/AC:L/Au:N/C:C/I:C/A:N

Name of the Vulnerable Software and Affected Versions Microsoft SharePoint Server (affected versions not specified) Microsoft SharePoint Enterprise Server (affected versions not specified)

Description An authentication bypass flaw exists due to weaknesses in how JSON Web Tokens (JWTs) are validated. A remote, unauthenticated attacker who possesses or enumerates a target user's Active Directory Security ID (SID) or User Principal Name (UPN) can bypass authentication checks. This allows the attacker to impersonate users, including administrators, to perform unauthorized actions, disclose files, and modify data. This issue can be chained with other vulnerabilities to achieve Remote Code Execution (RCE), which is the ability to execute arbitrary commands on a remote machine.

Recommendations At the moment, there is no information about a newer version that contains a fix for this vulnerability.

RCE

Weakness Enumeration

CWE-1390

Related Identifiers

BDU:2026-10845

CVE-2026-55040

Affected Products

Sharepoint Server

References · 26

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040 · Vendor Advisory
• https://bdu.fstec.ru/vul/2026-10845 · Security Note
• http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-55040 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2026-55040 · Security Note
• https://twitter.com/Securedotcom/status/2077376652540305412 · Twitter Post
• https://t.me/cKure/17376 · Telegram Post
• https://t.me/pentestbacklog/784 · Telegram Post
• https://reddit.com/r/pwnhub/comments/1uxdoko/microsoft_releases_record_622_security_patches · Reddit Post
• https://twitter.com/stephenfewer/status/2077120875401187683 · Twitter Post
• https://twitter.com/blackorbird/status/2077268390000132431 · Twitter Post
• https://twitter.com/techepages/status/2079152871376056736 · Twitter Post
• https://twitter.com/DFIR_Radar/status/2079009507234009301 · Twitter Post
• https://twitter.com/theluemmel/status/2077359808252932467 · Twitter Post
• https://t.me/secharvester/22893 · Telegram Post
• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-55040 · Note