How severe is CVE-2020-25577?

CVE-2020-25577 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2020-25577 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (71st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-25577?

CVE-2020-25577 primarily affects Freebsd. In total, 15 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-25577?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2020-25577 published?

CVE-2020-25577 was published on 2021-03-29 and last updated on 2026-06-17.

CVE-2020-25577

CVE-2020-25577 is a critical-severity vulnerability in Freebsd with a CVSS 3.x base score of 9.8. 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-120.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 10.0
EPSS exploit prediction: 1% (71st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-120
Affected product: Freebsd
Published: 2021-03-29
Last modified: 2026-06-17

Description

In FreeBSD 12.2-STABLE before r368250, 11.4-STABLE before r368253, 12.2-RELEASE before p1, 12.1-RELEASE before p11 and 11.4-RELEASE before p5 rtsold(8) does not verify that the RDNSS option does not extend past the end of the received packet before processing its contents. While the kernel currently ignores such malformed packets, it passes them to userspace programs. Any programs expecting the kernel to do validation may be vulnerable to an overflow.

Frequently asked questions

What is CVE-2020-25577?: In FreeBSD 12.2-STABLE before r368250, 11.4-STABLE before r368253, 12.2-RELEASE before p1, 12.1-RELEASE before p11 and 11.4-RELEASE before p5 rtsold(8) does not verify that the RDNSS option does not extend past the end of the received packet before processing its contents. While the kernel currently ignores such malformed packets, it passes them to userspace programs. Any programs expecting the kernel to do validation may be vulnerable to an overflow.
How severe is CVE-2020-25577?: CVE-2020-25577 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-25577 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (71st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-25577?: CVE-2020-25577 primarily affects Freebsd. In total, 15 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-25577?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2020-25577 published?: CVE-2020-25577 was published on 2021-03-29 and last updated on 2026-06-17.

References

Affected products (15)

cpe:2.3:o:freebsd:freebsd:11.4:-:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:11.4:p1:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:11.4:p2:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:11.4:p3:*:*:*:*:*:*
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:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:12.1:p3:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:12.1:p4:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:12.1:p5:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:12.1:p6:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:12.1:p7:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:12.1:p8:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:12.1:p9:*:*:*:*:*:*
cpe:2.3:o:freebsd:freebsd:12.2:-:*:*:*:*:*:*

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