How severe is CVE-2019-16216?

CVE-2019-16216 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2019-16216 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-16216?

CVE-2019-16216 affects Zulip Zulip Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2019-16216?

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

When was CVE-2019-16216 published?

CVE-2019-16216 was published on 2019-09-18 and last updated on 2026-06-17.

CVE-2019-16216

CVE-2019-16216 is a medium-severity vulnerability in Zulip Zulip Server with a CVSS 3.x base score of 5.4. 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-79.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
CVSS v2: 3.5
EPSS exploit prediction: 1% (48th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Zulip Zulip Server
Published: 2019-09-18
Last modified: 2026-06-17

Description

Zulip server before 2.0.5 incompletely validated the MIME types of uploaded files. A user who is logged into the server could upload files of certain types to mount a stored cross-site scripting attack on other logged-in users. On a Zulip server using the default local uploads backend, the attack is only effective against browsers lacking support for Content-Security-Policy such as Internet Explorer 11. On a Zulip server using the S3 uploads backend, the attack is confined to the origin of the configured S3 uploads hostname and cannot reach the Zulip server itself.

Frequently asked questions

What is CVE-2019-16216?: Zulip server before 2.0.5 incompletely validated the MIME types of uploaded files. A user who is logged into the server could upload files of certain types to mount a stored cross-site scripting attack on other logged-in users. On a Zulip server using the default local uploads backend, the attack is only effective against browsers lacking support for Content-Security-Policy such as Internet Explorer 11. On a Zulip server using the S3 uploads backend, the attack is confined to the origin of the configured S3 uploads hostname and cannot reach the Zulip server itself.
How severe is CVE-2019-16216?: CVE-2019-16216 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2019-16216 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-16216?: CVE-2019-16216 affects Zulip Zulip Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2019-16216?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2019-16216 published?: CVE-2019-16216 was published on 2019-09-18 and last updated on 2026-06-17.

References

Affected products (1)

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

More vulnerabilities in Zulip Zulip Server

CVE-2019-18933 — Critical (CVSS 9.8): In Zulip Server versions from 1.7.0 to before 2.0.7, a bug in the new user signup process meant that users who…
CVE-2020-15070 — High (CVSS 8.8): Zulip Server 2.x before 2.1.7 allows eval injection if a privileged attacker were able to write directly to the…
CVE-2017-0910 — High (CVSS 8.8): In Zulip Server before 1.7.1, on a server with multiple realms, a vulnerability in the invitation system lets an…
CVE-2025-31478 — High (CVSS 8.2): Zulip is an open-source team collaboration tool. Zulip supports a configuration where account creation is limited…
CVE-2023-33186 — High (CVSS 8.2): Zulip is an open-source team collaboration tool with unique topic-based threading that combines the best of email and…
CVE-2024-36612 — High (CVSS 7.5): Zulip from 8.0 to 8.3 contains a memory leak vulnerability in the handling of popovers.

All CVEs affecting Zulip Zulip Server →

Other CWE-79 (Cross-site Scripting (XSS)) vulnerabilities

CVE-2025-49410 — Critical (CVSS 10.0): Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Imran Emu TC…
CVE-2024-47875 — Critical (CVSS 10.0): DOMPurify is a DOM-only, super-fast, uber-tolerant XSS sanitizer for HTML, MathML and SVG. DOMpurify was vulnerable to…
CVE-2024-6886 — Critical (CVSS 10.0): Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in Gitea…
CVE-2023-45144 — Critical (CVSS 10.0): com.xwiki.identity-oauth:identity-oauth-ui is a package to aid in building identity and service providers based on…
CVE-2023-45138 — Critical (CVSS 10.0): Change Request is an pplication allowing users to request changes on a wiki without publishing the changes directly.…
CVE-2022-4361 — Critical (CVSS 10.0): Keycloak, an open-source identity and access management solution, has a cross-site scripting (XSS) vulnerability in the…

Browse all CWE-79 (Cross-site Scripting (XSS)) vulnerabilities →