CVE-2026-26861
CVE-2026-26861 is a high-severity vulnerability in Clevertap Clevertap Web Sdk with a CVSS 3.x base score of 8.3. 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-346.
Key facts
- Severity: High (CVSS 3.x base score 8.3)
- EPSS exploit prediction: 0% (8th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-9038
- Weakness: CWE-346
- Affected product: Clevertap Clevertap Web Sdk
- Published:
- Last modified:
Description
CleverTap Web SDK version 1.15.2 and earlier is vulnerable to Cross-Site Scripting (XSS) via window.postMessage. The handleCustomHtmlPreviewPostMessageEvent function in src/util/campaignRender/nativeDisplay.js performs insufficient origin validation using the includes() method, which can be bypassed by an attacker using a subdomain
Frequently asked questions
- What is CVE-2026-26861?
- CleverTap Web SDK version 1.15.2 and earlier is vulnerable to Cross-Site Scripting (XSS) via window.postMessage. The handleCustomHtmlPreviewPostMessageEvent function in src/util/campaignRender/nativeDisplay.js performs insufficient origin validation using the includes() method, which can be bypassed by an attacker using a subdomain
- How severe is CVE-2026-26861?
- CVE-2026-26861 has a CVSS 3.x base score of 8.3, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability low.
- Is CVE-2026-26861 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (8th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-26861?
- CVE-2026-26861 affects Clevertap Clevertap Web Sdk. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2026-26861?
- 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.
- Does CVE-2026-26861 have an EU (EUVD) identifier?
- Yes. CVE-2026-26861 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-9038.
- When was CVE-2026-26861 published?
- CVE-2026-26861 was published on 2026-02-27 and last updated on 2026-06-17.
References
- https://github.com/CleverTap/clevertap-web-sdk/blob/cf1b65d/src/util/campaignRender/nativeDisplay.js#L118-L121
- https://github.com/CleverTap/clevertap-web-sdk/issues/424
- https://github.com/CleverTap/clevertap-web-sdk/pull/417
Affected products (1)
- cpe:2.3:a:clevertap:clevertap_web_sdk:*:*:*:*:*:*:*:*
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