How severe is CVE-2021-33056?

CVE-2021-33056 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 none, and availability high.

Is CVE-2021-33056 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33056?

CVE-2021-33056 affects Linphone Belle-sip. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-33056?

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-2021-33056 published?

CVE-2021-33056 was published on 2021-08-12 and last updated on 2026-06-17.

CVE-2021-33056

CVE-2021-33056 is a high-severity vulnerability in Linphone Belle-sip 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-444.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 1% (67th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-444
Affected product: Linphone Belle-sip
Published: 2021-08-12
Last modified: 2026-06-17

Description

Belledonne Belle-sip before 4.5.20, as used in Linphone and other products, can crash via an invalid From header in a SIP message.

Frequently asked questions

What is CVE-2021-33056?: Belledonne Belle-sip before 4.5.20, as used in Linphone and other products, can crash via an invalid From header in a SIP message.
How severe is CVE-2021-33056?: CVE-2021-33056 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 none, and availability high.
Is CVE-2021-33056 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33056?: CVE-2021-33056 affects Linphone Belle-sip. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-33056?: 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-2021-33056 published?: CVE-2021-33056 was published on 2021-08-12 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:linphone:belle-sip:*:*:*:*:*:*:*:*

More vulnerabilities in Linphone Belle-sip

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