What’s Vulnerable › Vulnerabilities

CVE-2025-10148: predictable WebSocket mask

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-09-12 · updated 2026-10-19
• Weakness: CWE-340

Description

curl's WebSocket code did not update the 32-bit mask pattern for each new outgoing frame as the specification says. Instead it used a fixed mask that persisted and was used throughout the entire connection. A predictable mask pattern allows for a malicious server to induce traffic between the two communicating parties that could be interpreted by an involved proxy (configured or transparent) as genuine, real, HTTP traffic with content and thereby poison its cache. That cached poisoned content could then be served to all users of that proxy.

Affected products

• curl: from 8.11.0 before 8.16.0 — fixed in 8.16.0

How to fix

Upgrade to a fixed version: curl 8.16.0. Check the vendor advisory for mitigations.

References

• https://curl.se/docs/CVE-2025-10148.html
• https://curl.se/docs/CVE-2025-10148.json
• https://hackerone.com/reports/3330839
• http://www.openwall.com/lists/oss-security/2025/09/10/2
• http://www.openwall.com/lists/oss-security/2025/09/10/3
• http://www.openwall.com/lists/oss-security/2025/09/10/4

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