How severe is CVE-2021-30478?

CVE-2021-30478 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2021-30478 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-30478?

CVE-2021-30478 affects Zulip Zulip Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-30478?

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

When was CVE-2021-30478 published?

CVE-2021-30478 was published on 2021-04-15 and last updated on 2026-06-17.

CVE-2021-30478

CVE-2021-30478 is a medium-severity vulnerability in Zulip Zulip Server with a CVSS 3.x base score of 4.3. 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-269.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
CVSS v2: 4.0
EPSS exploit prediction: 1% (43rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-269
Affected product: Zulip Zulip Server
Published: 2021-04-15
Last modified: 2026-06-17

Description

An issue was discovered in Zulip Server before 3.4. A bug in the implementation of the can_forge_sender permission (previously is_api_super_user) resulted in users with this permission being able to send messages appearing as if sent by a system bot, including to other organizations hosted by the same Zulip installation.

Frequently asked questions

What is CVE-2021-30478?: An issue was discovered in Zulip Server before 3.4. A bug in the implementation of the can_forge_sender permission (previously is_api_super_user) resulted in users with this permission being able to send messages appearing as if sent by a system bot, including to other organizations hosted by the same Zulip installation.
How severe is CVE-2021-30478?: CVE-2021-30478 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2021-30478 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-30478?: CVE-2021-30478 affects Zulip Zulip Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-30478?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-30478 published?: CVE-2021-30478 was published on 2021-04-15 and last updated on 2026-06-17.

References

https://blog.zulip.com/2021/04/14/zulip-server-3-4/

Affected products (1)

cpe:2.3:a:zulip:zulip_server:*:*:*:*:*:*:*:*

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