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01 Record

CVE-2021-42756

Multiple stack-based buffer overflow vulnerabilities [CWE-121] in the proxy daemon of FortiWeb 5.x all versions, 6.0.7 and below, 6.1.2 and below, 6.2.6 and below, 6.3.16 and below, 6.4 all versions

CriticalPUBLISHEDCNA: fortinet
CNA base score9.3 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:U/RC:C

02 Description

Multiple stack-based buffer overflow vulnerabilities [CWE-121] in the proxy daemon of FortiWeb 5.x all versions, 6.0.7 and below, 6.1.2 and below, 6.2.6 and below, 6.3.16 and below, 6.4 all versions

03 Exploitation and scoring

Exploitation
Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.
SSVC decision
  • ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
  • AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
  • Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
34.97% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 98.2% of scored records. A rank, not a probability.
NVD base score
9.8 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD analysis status
Modified. NVD last modified this record on 2026-06-17.
Red Hat severity
No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2023-02-16 18:05Z3 YR AGO
Last updated
2024-10-23 14:49Z2 YR AGO
Reserved
2021-10-20
Assigning CNA
fortinet
Record state
PUBLISHED
Severity
Critical (CVSS 9.3)
CNA CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:U/RC:C
Weaknesses
  • CWE-121Stack-based Buffer OverflowVariant
  • CWE-787Out-of-bounds WriteBase
Data version
5.1
Document digest
301885ab05f42a3a3c0d658f775c3eba5068711a25f82c577770e22e3bf0fb0e

05 Affected products

VendorProductVersionsPlatforms
FortinetFortiWeb6.4.0 to 6.4.1, 6.3.0 to 6.3.16, 6.2.0 to 6.2.6, 6.1.0 to 6.1.2, 6.0.0 to 6.0.7, 5.9.0 to 5.9.1, 5.8.5 to 5.8.7, 5.8.0 to 5.8.3, 5.7.0 to 5.7.3, 5.6.0 to 5.6.2, 5.8.0 to < 5.8.*, 5.7.0 to < 5.7.*, 5.6.0 to < 5.6.*—

06 References

07 Remediation

Upgrade to FortiWeb 7.0.0 or above, Upgrade to FortiWeb 6.3.17 or above, Upgrade to FortiWeb 6.2.7 or above. Upgrade to FortiWeb 6.1.3 or above. Upgrade to FortiWeb 6.0.8 or above.