Vulnerabilities
CVE-2020-12819 — A heap-based buffer overflow vulnerability in the processing of Link Control Protocol messages in FortiGate v…
CVE-2020-12819 · FortiOS · CVSS 7.5
In brief
Summary
A heap-based buffer overflow vulnerability in the processing of Link Control Protocol messages in FortiGate versions 5.6.12, 6.0.10, 6.2.4 and 6.4.1 and earlier may allow a remote attacker with valid SSL VPN credentials to crash the SSL VPN daemon by sending a large LCP packet, when tunnel mode is enabled. Arbitrary code execution may be theoretically possible, albeit practically very difficult to achieve in this context
Weakness: CWE-122, CWE-787
Title, description and the vendor's statements are quoted from the CVE record; a vendor's advisory is summarised in Patcharo's words, with a link.
Affected and fixed versions
Per product and release branch, as the vendor's CVE record and official advisory state them. A fixed release is shown only when a document names it: the vendor's, or CERT-FR's for Check Point, with its source.
4 branches with a published fixed release
Fortinet FortiOS
Source: CVE-2020-12819
- 6.4End of lifeAffected versions6.4.0 – 6.4.1First fixed release6.4.2
- 6.2End of lifeAffected versions6.2.0 – 6.2.4First fixed release6.2.5
- 6.0End of lifeAffected versions6.0.0 – 6.0.10First fixed release6.0.11
- 5.6End of lifeAffected versions5.6.0 – 5.6.12First fixed release5.6.13
Releases the vendor does not list are not affected.
Remediation
Fix available
Vendor fix
- FortiOS 6.46.4.2
- FortiOS 6.26.2.5
- FortiOS 6.06.0.11
- FortiOS 5.65.6.13
Upgrade to a fixed release listed above for your branch, or to a later fixed release the vendor explicitly supports.
Please upgrade to FortiOS versions 5.6.13 or above. Please upgrade to FortiOS versions 6.0.11 or above. Please upgrade to FortiOS versions 6.2.5 or above. Please upgrade to FortiOS versions 6.4.2 or above. Workaround: Disable tunnel mode.
SourceFortinet (CVE record)
Vendor advisory
Last verified 1 Oct 2026 at 09:30 UTC
Known exploitation
Not listed in CISA KEV as of the last check.
0.79% probability of exploitation in the next 30 days (percentile 55%).
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
CERT-FR
No CERT-FR advisory or alert of the last two years references this CVE, for the vendors Patcharo covers.
Timeline
- Published by the source
- Source record last modified
- EPSS score computed
- Last verified by Patcharo
Official sources
- Fortinet (CVE record)retrieved 1 Oct 2026 at 09:30 UTC
- NVDretrieved 27 Sept 2026 at 23:44 UTC
- FIRST EPSSretrieved 30 Sept 2026 at 00:17 UTC
Fortinet · NVD · FIRST EPSS
How Patcharo reads this
Affected and fixed releases come from the vendor's structured statements and are matched against exact versions; CVSS from NVD, exploitation from CISA KEV and the vendor's own advisory, probability from FIRST EPSS. Missing data stays Unknown and never becomes Not affected.
Read the methodologyRead the guide: FortiOS version numbering: branches, patch releases and the Feature and Mature labels
Related vulnerabilities
Other records affecting the same products, newest first.
- CVE-2026-71407A Stack-based Buffer Overflow vulnerability [CWE-121] vulnerability in Fortinet FortiOS 7.6.1 through 7.6.6 m…High
- CVE-2025-53844A out-of-bounds write vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, For…High
- CVE-2025-53847A missing authentication for critical function vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS…High
- CVE-2025-68686Fortinet FortiOS Exposure of Sensitive Information to an Unauthorized Actor VulnerabilityMediumKEV
- CVE-2025-64157A use of externally-controlled format string vulnerability in Fortinet FortiOS 7.6.0 through 7.6.4, FortiOS 7…High