CVE-2026-26861
Clevertap Web Sdk ≤ 1.15.2
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:LSummary
CVE-2026-26861 is a high-severity Origin Validation Error (CWE-346) vulnerability in Clevertap Clevertap Web Sdk. Its CVSS base score is 8.3 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique DHCP Spoofing (T1557.003); ranked at the 8th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to AC-4 (Information Flow Enforcement) and IA-3 (Device Identification and Authentication) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-26861 is a Cross-Site Scripting (XSS) vulnerability affecting CleverTap Web SDK versions 1.15.2 and earlier. The issue resides in the handleCustomHtmlPreviewPostMessageEvent function within src/util/campaignRender/nativeDisplay.js, where origin validation for window.postMessage events relies on the includes() method. This check can be bypassed by an attacker using a subdomain that partially matches the expected origin string, allowing malicious payloads to be processed.
The vulnerability has a CVSS v3.1 base score of 8.3 (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L), indicating it is exploitable over the network with low complexity and no privileges required, though user interaction is needed. A remote attacker can craft a malicious webpage on a controllable subdomain (e.g., attacker.example.com targeting example.com), then trick a user into visiting it while the vulnerable SDK is loaded on the target site. Upon user interaction, such as loading the page, the attacker sends a postMessage with a crafted origin, evading validation and injecting arbitrary JavaScript. This grants high-impact confidentiality and integrity violations, such as stealing session cookies or modifying page content, with low availability impact.
GitHub references detail the flaw and remediation: the vulnerable code is shown at lines 118-121 in nativeDisplay.js, issue #424 reports the problem, and pull request #417 provides the fix by improving origin validation. Security practitioners should advise updating the CleverTap Web SDK to a version incorporating this patch to mitigate the issue.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-9038
Vulnerability Data
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
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
—
—
- 3 hardening rules · 1 OS baseline
—
Mitigating Controls (NIST 800-53 r5) AI
Information flow enforcement directly requires validating the source of data before allowing transmission or receipt.
Device identification and authentication mandates verifying the source before establishing connections.
Session authenticity mechanisms require validation that communications originate from the expected party.
Boundary protection at interfaces enforces checks on the origin of incoming communications.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Authentication directly verifies the source of users/services/hardware, mitigating origin validation failures.
Verifying identity assertions enforces origin validation for conveyed claims.
Documenting authorized flows supports origin validation by defining expected sources.
Protecting networks from unauthorized access requires origin checks on communication sources.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Network security controls enforce origin validation at network boundaries.
Security of network services includes validating the authenticity of service endpoints.
Network segregation reduces exposure but does not directly validate origins.
Application security requirements explicitly call for origin validation of inputs and communications.
Secure architecture principles encourage origin checks but do not mandate them.
Secure coding practices include implementing proper origin validation to prevent spoofing.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (3 rules)
- V-248574 YUM must be configured to prevent the installation of patches, service packs, device drivers, or OL 8 system components that have not been digitally signed using a certificate that is recognized and approved by the organization. prevents CWE-346
- V-248575 OL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-346
- V-248827 OL 8 must not have the rsh-server package installed. prevents CWE-346