How severe is CVE-2021-35977?

CVE-2021-35977 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-2021-35977 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (72nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-35977?

CVE-2021-35977 primarily affects Digi Realport. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-35977?

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-2021-35977 published?

CVE-2021-35977 was published on 2021-10-08 and last updated on 2026-06-17.

CVE-2021-35977

CVE-2021-35977 is a critical-severity vulnerability in Digi Realport 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: 7.5
EPSS exploit prediction: 2% (72nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-120
Affected product: Digi Realport
Published: 2021-10-08
Last modified: 2026-06-17

Description

An issue was discovered in Digi RealPort for Windows through 4.8.488.0. A buffer overflow exists in the handling of ADDP discovery response messages. This could result in arbitrary code execution.

Frequently asked questions

What is CVE-2021-35977?: An issue was discovered in Digi RealPort for Windows through 4.8.488.0. A buffer overflow exists in the handling of ADDP discovery response messages. This could result in arbitrary code execution.
How severe is CVE-2021-35977?: CVE-2021-35977 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-2021-35977 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (72nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-35977?: CVE-2021-35977 primarily affects Digi Realport. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-35977?: 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-2021-35977 published?: CVE-2021-35977 was published on 2021-10-08 and last updated on 2026-06-17.

References

https://raw.githubusercontent.com/reidmefirst/vuln-disclosure/main/2021-02.txt

Affected products (19)

cpe:2.3:a:digi:realport:*:*:*:*:*:linux:*:*
cpe:2.3:a:digi:realport:*:*:*:*:*:windows:*:*
cpe:2.3:o:digi:connectport_ts_8\/16_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:connectport_lts_8\/16\/32_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:passport_integrated_console_server_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:cm_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:portserver_ts_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:portserver_ts_mei_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:portserver_ts_mei_hardened_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:portserver_ts_m_mei_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:6350-sr_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:portserver_ts_p_mei_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:transport_wr11_xt_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:one_iap_family_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:one_ia_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:wr31_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:wr44_r_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:connect_es_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:digi:wr21_firmware:*:*:*:*:*:*:*:*

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CVE-2021-36767 — Critical (CVSS 9.8): In Digi RealPort through 4.10.490, authentication relies on a challenge-response mechanism that gives access to the…
CVE-2023-4299 — Critical (CVSS 9.0): Digi RealPort Protocol is vulnerable to a replay attack that may allow an attacker to bypass authentication to access…
CVE-2021-35979 — High (CVSS 8.1): An issue was discovered in Digi RealPort through 4.8.488.0. The 'encrypted' mode is vulnerable to man-in-the-middle…

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