Home/CVE/FatFs R0.16 and earlier contains a downstream-caller vulnerability pattern associated with FatFs long filename handling.
CVE
CVE-2026-6688
FatFs R0.16 and earlier contains a downstream-caller vulnerability pattern associated with FatFs long filename handling.
FatFs R0.16 and earlier contains a downstream-caller vulnerability pattern associated with FatFs long filename handling. With LFN enabled, fno.fname can be up to 255 characters.
many callers copy it into short fixed buffers without bounds checks, causing overflow. This maps to CWE-120 (Buffer Copy without Checking Size of Input). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H (7.6, High). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.
HIGH · CVSS 7.6
EPSS 0.0019
EPSS exploitation odds0.19% · top 91%
Schedule remediation
- CVSS base score ≥ 7.0
No Sigma yet — build one →
YARA rules0
Look this up elsewhere - one-click external pivots
▸
How to read a CVE - triage first, then detect and patch
This page is every public fact about CVE-2026-6688, cross-linked. Its job is to answer one question fast - does this need my attention now? - and then hand you the two things you do about it. Here is how an analyst reads it.
Triage: should I act now? Four signals, and they are not interchangeable:
CVSSseverity - how bad it is IF exploited, 0-10. A high CVSS alone is not urgency; a flaw can be a perfect 10 and never actually be attacked.
EPSSprobability - a model’s estimate of the chance it is exploited in the next 30 days, 0-1. This is the “will it actually happen” signal.
CISA KEVconfirmed - it is being exploited in the wild right now. The strongest signal on the page; KEV beats any score.
Weaponisedavailability - public exploits / PoCs, and especially Metasploit modules rated Excellent / Great. Reliable, packaged exploit code means low-skill attackers can use it today.
How they combine: KEV, or a dependable Metasploit module, means patch now regardless of CVSS. High CVSS + low EPSS + no exploit is real but not an emergency - schedule it. Low CVSS but KEV-listed still gets patched now. The verdict above already weighed these for you; this is how it got there.
Then what - two workflows:
Detectwhen you cannot patch today, follow this CVE to the ATT&CK techniques it enables, then Build a SIEM detection (the green button) - author a rule, test it in Atomic, deploy it. That buys visibility while the patch waits.
PatchAffected products / packages tell you if you are exposed; Fixed versions by distribution and Vendor advisories give the exact version that closes it.
Reading order for the panels below: verdict + badges, then Public exploits / Metasploit (is it weaponised), then ATT&CK techniques + Sigma / IDS rules (can I detect it), then Affected products / packages + Fixed versions (am I exposed, what patches it), then Threat actors / IOCs (who uses it), then Scoring & timeline / references (the evidence).
CVSS base score
7.6
HIGHCVSS v3.1 · 44488dab-36db-4358-99f9-bc116477f914
EPSS exploitation probability
0.19%
Top 91%odds of exploitation in the next 30 days
CVSS metric silhouette
shape grows toward worst-case
SSVC triage · cisa-vulnrichment
Exploitation
poc
Automatable
no
Tech impact
total
CVSS vector breakdown
Exploitability - how they get in
Attack Vector
Network
Adjacent
Local
Physical
Attack Complexity
Low
High
Privileges Required
None
Low
High
User Interaction
None
Required
Scope
Unchanged
Changed
Impact - what breaks
Confidentiality
None
Low
High
Integrity
None
Low
High
Availability
None
Low
High
VECTOR
CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H◆
ATT&CK techniques
1Techniques this CVE enables. Pills with a solid outline are high confidence - named directly in ATT&CK or Nuclei, or human-curated by CTID; the rest are inferred from the weakness type using MITRE's CVE Mapping Methodology and the CWE → CAPEC chain. Broad, generic-weakness guesses are filtered out. A small N× marks a technique that N independent sources agree on.
▤ Build a SIEM detection for these techniques▤
CAPEC attack patterns
12Attack patterns this CVE enables - the bridge from weakness to ATT&CK technique.
CAPEC-CAPEC-10 · Buffer Overflow via Environment Variables CAPEC-CAPEC-100 · Overflow Buffers CAPEC-CAPEC-14 · Client-side Injection-induced Buffer Overflow CAPEC-CAPEC-24 · Filter Failure through Buffer Overflow CAPEC-CAPEC-42 · MIME Conversion CAPEC-CAPEC-44 · Overflow Binary Resource File CAPEC-CAPEC-45 · Buffer Overflow via Symbolic Links CAPEC-CAPEC-46 · Overflow Variables and Tags CAPEC-CAPEC-47 · Buffer Overflow via Parameter Expansion CAPEC-CAPEC-67 · String Format Overflow in syslog() CAPEC-CAPEC-8 · Buffer Overflow in an API Call CAPEC-CAPEC-9 · Buffer Overflow in Local Command-Line Utilities
⬡
Weakness Classification
▤
Related CVEs
4CVEs linked to this one by a shared weakness (CWE) or affected product - joins on data already in the engine, with the reason shown per row.
CVE-1999-0046
Buffer overflow of rlogin program using TERM environmental variable.
1
same CWE-120
CVE-1999-0038
Buffer overflow in xlock program allows local users to execute commands as root.
2
same CWE-120
HIGH
CVE-1999-0284
Denial of service to NT mail servers including Ipswitch, Mdaemon, and Exchange t...
3
same CWE-120
CVE-1999-0385
The LDAP bind function in Exchange 5.5 has a buffer overflow that allows a remot...
same CWE-120
🔗
References & Sources
4Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.