Threats / Microsoft / CVE-2025-53770
CVE-2025-53770
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Microsoft SharePoint vulnerability
Microsoft SharePoint Server on-premises contains a deserialization vulnerability (CWE-502) allowing remote code execution. This is a patch bypass for CVE-2025-49704 and is actively exploited in ransomware campaigns.
Verdict
Today item, not a backlog item.
Critical remote code execution vulnerability in SharePoint on-premises via unsafe deserialization. High exploitation activity and ransomware deployment observed. Patch bypass status indicates previous mitigations were insufficient.
CISA KEV Yes · 2025-07-203Ransomware use Flagged3EPSS 0.99982 (verify live)4Exploit Weaponized · public PoC5
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Fully weaponized — public exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
199 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2025-07-20), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.99982 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Microsoft, SharePoint. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-502 Deserialization of Untrusted Data — weakness family: Injection.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious serialized object and send it to an unauthenticated SharePoint endpoint.
Business
Attacker gains initial network access to a core collaboration platform without authentication.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I exploit unsafe deserialization to execute arbitrary code with SharePoint service privileges.
Business
Attacker achieves code execution within the trusted security context of the SharePoint application.
3
Lateral reach — past segmentation narrative 3
Attacker
I establish persistence and lateral movement across the on-premises infrastructure.
Business
Attacker pivots to sensitive data repositories and domain resources accessible from SharePoint.
4
Data at risk — exfiltration narrative 4
Attacker
I deploy ransomware payloads across connected systems and encrypt business-critical data.
Business
Operations halt; data becomes inaccessible; ransom demands issued; recovery costs and downtime escalate.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05