Threats / Microsoft / CVE-2025-21391
CVE-2025-21391
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Microsoft Windows vulnerability
Microsoft Windows Storage contains a link following vulnerability enabling privilege escalation and potential data deletion or service disruption.
Verdict
Today item — known-exploited.
A link following flaw in Windows Storage allows attackers to escalate privileges and delete data, potentially causing service unavailability. Active exploitation observed in the wild.
CISA KEV Yes · 2025-02-115EPSS 0.02258 (verify live)6CVSS 7.13CISA SSVC Exploitation: active · Automatable: no · Impact: partial4
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
5 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 2025-02-11).
Probability (EPSS)
EPSS 0.02258 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 7.1 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H/E:F/RL:O/RC:C) · Affected: Microsoft, Windows. Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
Weakness (CWE)
Mapped to CWE-59 Link Following — weakness family: Path traversal / file.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog the same day the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
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 symbolic link or junction point in a location the Storage service will follow during its operations.
Business
Attacker gains elevated privileges by exploiting the service's trusted execution context.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I direct the Storage service to access or modify files outside its intended scope through the link.
Business
Critical data becomes accessible or modifiable by unprivileged actors, compromising data integrity.
3
Lateral reach — past segmentation narrative 3
Attacker
I delete essential storage-related files or configuration data via the escalated access path.
Business
Storage services become unavailable, disrupting dependent systems and business operations.
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