CVE-2021-42757: fortinet fortiadc Classic Buffer Overflow
CVSS: 6.7v3.1MediumModified
Published 08-12-2021Last modified 16-10-2025
Vulnerability summary
CVE-2021-42757 is a medium (CVSS 6.7) Classic Buffer Overflow vulnerability in fortinet fortiadc. EPSS estimates a 0.52% chance of exploitation in the next 30 days, higher than 42.7% of scored vulnerabilities.
CVSS score
6.7/10
010
Medium · v3.1 (NVD)EPSS score
0.52%
0%100%
Low · +0.04 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Timeline
- 08-12-2021PublishedVulnerability first disclosed.
- 16-10-2025Last modifiedVulnerability information updated.
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.
CVSS metrics
3 scores · 2 sources · 2 versionsMedium 6.7Preferred score · NVD (NIST)
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:HSources2 sources · 6.3–6.7
- CVE.orgCNA6.3MediumCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H/E:P/RL:U/RC:CDiffers
Medium 4.6Preferred score · NVD (NIST)
AV:L/AC:L/Au:N/C:P/I:P/A:PSourcesSingle source
EPSS trend
Probability
0.52%
Chance of exploitation in the next 30 days
Percentile
43%
Versus all other CVEs
30-day change
+0.04 pp
From 0.48% on 20-09-2026
20-09-202620-10-2026
EPSS score0.52%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
- CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.
Affected systems
Fortinet15 products
- fortiadc≥ 6.1.0, ≤ 6.1.5 | ≥ 6.0.0, ≤ 6.0.4 | ≥ 5.4.0, ≤ 5.4.5 | ≥ 5.3.0, ≤ 5.3.7 | ≥ 5.2.0, ≤ 5.2.8 | ≥ 5.1.0, ≤ 5.1.7 | ≥ 5.0.0, ≤ 5.0.4 | ≥ 5.0.0, ≤ 6.1.5 | ≥ 6.2.0, ≤ 6.2.2
- fortianalyzer≥ 6.4.0, ≤ 6.4.7 | ≥ 6.2.0, ≤ 6.2.13 | ≥ 6.0.0, ≤ 6.0.12 | ≥ 6.0.0, ≤ 6.4.7 | ≥ 7.0.0, ≤ 7.0.2
- fortiddos≥ 5.5.0, ≤ 5.5.1 | ≥ 5.4.0, ≤ 5.4.3 | ≥ 5.3.0, ≤ 5.3.2 | 5.2.0 | 5.1.0 | 5.0.0 | 4.7.0 | 4.6.0 | 4.5.0 | ≥ 4.4.0, ≤ 4.4.2
- fortiddos-f≥ 6.4.0, ≤ 6.4.1 | 6.3.0 | ≥ 6.2.0, ≤ 6.2.2 | ≥ 6.1.0, ≤ 6.1.4
- fortimail≥ 6.2.0, ≤ 6.2.7 | ≥ 6.0.0, ≤ 6.0.12 | ≥ 5.4.0, ≤ 5.4.12 | ≥ 5.4.0, ≤ 6.2.7 | ≥ 6.4.0, ≤ 6.4.6 | ≥ 7.0.0, ≤ 7.0.2
1 vendor · 15 products
References
1 links- fortiguard.com/advisory/FG-IR-21-173Vendor Advisory