How severe is CVE-2020-7451?

CVE-2020-7451 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2020-7451 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (63rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-7451?

CVE-2020-7451 primarily affects Freebsd. In total, 10 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-7451?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2020-7451 published?

CVE-2020-7451 was published on 2020-04-28 and last updated on 2026-06-17.

CVE-2020-7451

CVE-2020-7451 is a medium-severity vulnerability in Freebsd with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-908.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v2: 5.0
EPSS exploit prediction: 1% (63rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-908
Affected product: Freebsd
Published: 2020-04-28
Last modified: 2026-06-17

Description

In FreeBSD 12.1-STABLE before r358739, 12.1-RELEASE before 12.1-RELEASE-p3, 11.3-STABLE before r358740, and 11.3-RELEASE before 11.3-RELEASE-p7, a TCP SYN-ACK or challenge TCP-ACK segment over IPv6 that is transmitted or retransmitted does not properly initialize the Traffic Class field disclosing one byte of kernel memory over the network.

Frequently asked questions

What is CVE-2020-7451?: In FreeBSD 12.1-STABLE before r358739, 12.1-RELEASE before 12.1-RELEASE-p3, 11.3-STABLE before r358740, and 11.3-RELEASE before 11.3-RELEASE-p7, a TCP SYN-ACK or challenge TCP-ACK segment over IPv6 that is transmitted or retransmitted does not properly initialize the Traffic Class field disclosing one byte of kernel memory over the network.
How severe is CVE-2020-7451?: CVE-2020-7451 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2020-7451 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (63rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-7451?: CVE-2020-7451 primarily affects Freebsd. In total, 10 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-7451?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2020-7451 published?: CVE-2020-7451 was published on 2020-04-28 and last updated on 2026-06-17.

References

https://security.FreeBSD.org/advisories/FreeBSD-SA-20:04.tcp.asc

Affected products (10)

cpe:2.3:o:freebsd:freebsd:11.3:-:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:11.3:p1:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:11.3:p2:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:11.3:p3:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:11.3:p4:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:11.3:p5:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:11.3:p6:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:12.1:-:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:12.1:p1:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:12.1:p2:*:*:*:*:*:*

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