How severe is CVE-2026-33978?

CVE-2026-33978 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-33978 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-33978?

CVE-2026-33978 primarily affects Streetwriters Notesnook Mobile. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-33978?

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

Does CVE-2026-33978 have an EU (EUVD) identifier?

Yes. CVE-2026-33978 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-17962.

When was CVE-2026-33978 published?

CVE-2026-33978 was published on 2026-04-01 and last updated on 2026-06-17.

CVE-2026-33978

CVE-2026-33978 is a medium-severity vulnerability in Streetwriters Notesnook Mobile 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)
EPSS exploit prediction: 0% (20th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-17962
Weakness: CWE-79
Affected product: Streetwriters Notesnook Mobile
Published: 2026-04-01
Last modified: 2026-06-17

Description

Notesnook is a note-taking app focused on user privacy & ease of use. Prior to version 3.3.17, a stored XSS vulnerability exists in the mobile share / web clip flow because attacker-controlled clip metadata is concatenated into HTML without escaping and then rendered with innerHTML inside the mobile share editor WebView. An attacker can control the shared title metadata (for example through Android/iOS share metadata such as TITLE / SUBJECT, or through link-preview title data) and inject HTML such as </a><img src=x onerror=...>. When the victim opens the Notesnook share flow and selects Web clip, the payload is inserted into the generated HTML and executed in the mobile editor WebView. This issue has been patched in version 3.3.17.

Frequently asked questions

What is CVE-2026-33978?: Notesnook is a note-taking app focused on user privacy & ease of use. Prior to version 3.3.17, a stored XSS vulnerability exists in the mobile share / web clip flow because attacker-controlled clip metadata is concatenated into HTML without escaping and then rendered with innerHTML inside the mobile share editor WebView. An attacker can control the shared title metadata (for example through Android/iOS share metadata such as TITLE / SUBJECT, or through link-preview title data) and inject HTML such as </a><img src=x onerror=...>. When the victim opens the Notesnook share flow and selects Web clip, the payload is inserted into the generated HTML and executed in the mobile editor WebView. This issue has been patched in version 3.3.17.
How severe is CVE-2026-33978?: CVE-2026-33978 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-33978 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-33978?: CVE-2026-33978 primarily affects Streetwriters Notesnook Mobile. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-33978?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-33978 have an EU (EUVD) identifier?: Yes. CVE-2026-33978 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-17962.
When was CVE-2026-33978 published?: CVE-2026-33978 was published on 2026-04-01 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:streetwriters:notesnook_mobile:*:*:*:*:*:android:*:*
cpe:2.3:a:streetwriters:notesnook_mobile:*:*:*:*:*:iphone_os:*:*

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