CVE-2025-25249
CVE-2025-25249 is a security flaw in Fortinet products, Fortinet’s business security equipment. Attackers can corrupt memory in Fortinet products, which they use to take it over. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 9 Sep 2026.[1]
Fortinet products is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Fortinet has published a fix or advice.
Description
CISA calls it a heap-based buffer overflow in Fortinet Multiple Products. In its words: “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.”[1]
The CVE record adds: “A heap-based buffer overflow vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, FortiOS 7.2.0 through 7.2.11, FortiOS 7.0.0 through 7.0.17, FortiOS 6.4 all versions, FortiSwitchManager 7.2.0 through 7.2.6, FortiSwitchManager 7.0.0 through 7.0.5 allows attacker to execute unauthorized code or commands via specially crafted packets”[2]
The underlying weakness is heap buffer overflow (CWE-122), out-of-bounds write (CWE-787), in MITRE’s list of common software weaknesses.
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Fortinet’s advisory has them[3]. CISA names the product as Fortinet Multiple Products.
Most families won’t have Fortinet products; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 9 Sep 2026, 239 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 12 Sep 2026 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 4%. That’s in the top 11% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Fortinet has published a fix or advice.[3] CISA’s required action: “Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes).”[1]
- Check whether you use it.Fortinet products is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 12 Sep 2026 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 4%.[4] |
See also
Other Fortinet products flaws
- CVE-2025-61624: path traversal ·
- CVE-2026-24858: authentication bypass using an alternate path or channel ·
- CVE-2025-59718: improper verification of cryptographic signature ·
- CVE-2025-32756: stack-based buffer overflow ·
- CVE-2024-23113: format string ·
- CVE-2022-40684: authentication bypass ·
Other Fortinet flaws
- CVE-2026-104286, Fortinet FortiMail: path traversal ·
- CVE-2025-68686, Fortinet FortiOS: exposure of sensitive information to an unauthorized actor ·
- CVE-2026-39808, Fortinet FortiSandbox: OS command injection ·
- CVE-2026-25089, Fortinet FortiSandbox: OS command injection ·
- CVE-2026-21643, Fortinet FortiClient EMS: SQL injection ·
Other heap buffer overflow flaws
- CVE-2026-94127, F5 BIG-IP APM: heap-based buffer overflow ·
- CVE-2026-85880, Microsoft Windows: heap-based buffer overflow ·
- CVE-2025-32706, Microsoft Windows: common log file system (CLFS) driver heap-based buffer overflow ·
- CVE-2025-24993, Microsoft Windows: NTFS heap-based buffer overflow ·
- CVE-2025-21418, Microsoft Windows: ancillary function driver for winSock heap-based buffer overflow ·
Added the same day
- CVE-2026-87491, Chrome and other Chromium browsers: out of bounds write ·
- CVE-2026-20079, Cisco Secure Firewall Management Center (FMC) and Security Cloud Control (SCC) Firewall Management: firewall management center authentication bypass using an alternate path or channel ·
- CVE-2026-19490, Citrix NetScaler: authentication bypass using an alternate path or channel ·
Every Fortinet flaw on CISA’s list · Everything added in September 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “Fortinet Multiple Products Heap-based Buffer Overflow Vulnerability”. Known Exploited Vulnerabilities Catalog, added 9 Sep 2026.
- ^ National Institute of Standards and Technology. “CVE-2025-25249 Detail”. National Vulnerability Database, published 13 Jan 2026.
- ^ Fortinet. Advisories and fixes: fortiguard.fortinet.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.037, percentile 89.9, 31 Oct 2026.
- CVE Program. “CVE-2025-25249”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.