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Cloudflare's handling of a bug in interpreting IPv4-mapped IPv6 addresses

Blog post from Cloudflare

Post Details
Company
Date Published
Author
Lucas Ferreira, Aki Shugaeva, Yuchen Wu
Word Count
1,091
Company Posts That Month
13
Language
English
Hacker News Points
8
Post removed?
No
Summary

In November 2022, a critical vulnerability was reported to Cloudflare's bug bounty program. The issue involved using DNS records based on IPv4-mapped IPv6 addresses to bypass network policies and access ports on loopback addresses of servers. Upon receiving the report, Cloudflare's Security Incident Response Team (SIRT) quickly deployed a hotpatch within three hours to prevent exploitation. An investigation revealed that the vulnerability was caused by two bugs in their internal DNS and HTTP systems. To remediate the issue, a fix was implemented in the proxy service to validate IP addresses correctly. No evidence of previous exploitation was found, and regular security reviews and audits continue to enhance Cloudflare's services.

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