How severe is CVE-2019-3977?

CVE-2019-3977 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2019-3977 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-3977?

CVE-2019-3977 primarily affects Mikrotik Routeros. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-3977?

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

When was CVE-2019-3977 published?

CVE-2019-3977 was published on 2019-10-29 and last updated on 2026-06-17.

CVE-2019-3977

CVE-2019-3977 is a high-severity vulnerability in Mikrotik Routeros with a CVSS 3.x base score of 7.5. 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-494.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 8.5
EPSS exploit prediction: 1% (60th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-494
Affected product: Mikrotik Routeros
Published: 2019-10-29
Last modified: 2026-06-17

Description

RouterOS 6.45.6 Stable, RouterOS 6.44.5 Long-term, and below insufficiently validate where upgrade packages are download from when using the autoupgrade feature. Therefore, a remote attacker can trick the router into "upgrading" to an older version of RouterOS and possibly reseting all the system's usernames and passwords.

Frequently asked questions

What is CVE-2019-3977?: RouterOS 6.45.6 Stable, RouterOS 6.44.5 Long-term, and below insufficiently validate where upgrade packages are download from when using the autoupgrade feature. Therefore, a remote attacker can trick the router into "upgrading" to an older version of RouterOS and possibly reseting all the system's usernames and passwords.
How severe is CVE-2019-3977?: CVE-2019-3977 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2019-3977 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-3977?: CVE-2019-3977 primarily affects Mikrotik Routeros. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-3977?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2019-3977 published?: CVE-2019-3977 was published on 2019-10-29 and last updated on 2026-06-17.

References

https://www.tenable.com/security/research/tra-2019-46

Affected products (2)

cpe:2.3:o:mikrotik:routeros:*:*:*:*:ltr:*:*:*
cpe:2.3:o:mikrotik:routeros:*:*:*:*:-:*:*:*

More vulnerabilities in Mikrotik Routeros

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CVE-2023-30799 — Critical (CVSS 9.1): MikroTik RouterOS stable before 6.49.7 and long-term through 6.48.6 are vulnerable to a privilege escalation issue. A…
CVE-2018-14847 — Critical (CVSS 9.1): MikroTik RouterOS through 6.42 allows unauthenticated remote attackers to read arbitrary files and remote authenticated…
CVE-2022-45313 — High (CVSS 8.8): Mikrotik RouterOs before stable v7.5 was discovered to contain an out-of-bounds read in the hotspot process. This…

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Threat intelligence

Threat-intel indicators referencing this CVE:

35.130.111.146 (ipv4-addr)
35.130.111.98 (ipv4-addr)
27.110.176.222 (ipv4-addr)