Several Fortinet products: a memory flaw attackers can abuse
OFFICIAL NAME: Fortinet Multiple Products Heap-based Buffer Overflow Vulnerability
WHAT IT IS · VPN, FIREWALL OR GATEWAYIt sits at the edge of your network and faces the internet, so attackers can reach it directly.
DO THIS FIRSTIf you have it, patch it today. If you cannot, block access to it from the internet until you can. Not sure if you use it? Send this page to your IT provider or security lead and ask.
TECHNICAL SUMMARY Fortinet FortiOS, FortiSwitchManager, and FortiSASE contain a heap-based buffer overflow vulnerability that allows an attacker to execute unauthorized code or commands via specially crafted packets.
WHY THIS VERDICT Attacks are confirmed. The vulnerability is 299 days old, so many systems are likely still unpatched.
WHY IT RANKS HERE Exploitation is confirmed by an authoritative source. The product faces the internet or gives remote access.
- HIGHEST CONFIRMED RUNG
- EXPLOITED
- CISA KEV
- LISTED
- EXPLOIT CODE
- NONE KNOWN
How far has it climbed?
01 TALK
□ NO EVIDENCE YETNEWEST EVIDENCE NONE YETNo evidence yet.
SRC: NONE YET02 EXPOSED
□ NOT TRACKED YETNO SOURCE FOR THIS STEP YETWe have no source that counts exposed systems yet. Internet scan data needs a partnership we do not have. No evidence here does not mean nothing is exposed.
03 TRIED
■ CONFIRMEDNEWEST EVIDENCE · 2 INDEPENDENT SOURCESAttacks that worked are confirmed (step 4), so attempts count as confirmed too.
04 EXPLOITED
■ CONFIRMEDNEWEST EVIDENCE · 2 INDEPENDENT SOURCESFortinet FortiOS, FortiSwitchManager, and FortiSASE contain a heap-based buffer overflow vulnerability that allows an attacker to execute unauthorized code or commands via specially crafted packets. CISA Vulnrichment marks CVE-2025-25249 as actively exploited.
05 DAMAGE
□ NOT TRACKED YETNO SOURCE FOR THIS STEP YETBreach notices and filings rarely name the flaw that was used, so we cannot link them to this event yet. No evidence here does not mean no harm.
When each thing happened
- DISCLOSED
- EXPLOIT CODE PUBLICNOT YET
- FIRST ATTACK REPORT
- CISA KEV LISTING
- US FEDERAL DEADLINE
THE FIX
CISA's instruction: apply the vendor's fix, or stop using the product if no fix exists. The deadline CISA set for US federal agencies, Sep 12, 2026, has passed. It is a US government deadline; use it as a guide.
Questions to ask this week
- Do we run Several Fortinet products? If yes, is it patched or cut off from the internet?
- Who owns fixing it, and by what date?
- Have we checked for signs of attack since the first report, not just since the patch?
How it unfolded
- Attack activity. JAN 13, 2026CISA Vulnrichment marks CVE-2025-25249 as actively exploited
- Attack activity. SEP 8, 2026Fortinet Multiple Products Heap-based Buffer Overflow Vulnerability