The Internet Is Falling Down, Falling Down, Falling Down cPa...

[carlospolop]

🤖 Automated Content Update

This PR was automatically generated by the HackTricks News Bot based on a technical blog post.

📝 Source Information

• Blog URL: https://labs.watchtowr.com/the-internet-is-falling-down-falling-down-falling-down-cpanel-whm-authentication-bypass-cve-2026-41940
• Blog Title: The Internet Is Falling Down, Falling Down, Falling Down: cPanel & WHM Authentication Bypass CVE-2026-41940
• Suggested Section: Network Services Pentesting → 80,443 - Pentesting Web → Login Bypass, with cross-references to CRLF Injection and Cache Poisoning and Cache Deception

🎯 Content Summary

Scope, severity, and impact. CVE-2026-41940 is a critical, remotely reachable pre-authentication authentication bypass in cPanel & WHM session loading and saving. WHM is the root-level administrative interface for shared-hosting servers, while cPanel is the user-facing panel for individual hosting accounts. The article describes cPanel as managing more than 70 million domains and cites KnownHost confirmation that exploitation was occurring in the wild against the hosting ...

🔧 Technical Details

Optional-secret bypass combined with CRLF session injection. Applications that serialize session hashes as line-oriented key=value\r\n records must sanitize every attacker-controlled value before writing it. A dangerous design occurs when the writer relies on callers to invoke the sanitizer and when an optional cookie suffix controls whether a value is encoded. In this case, the Basic Authentication password was decoded from the Authorization header and only NUL bytes were removed, so CRLF survived. The attacker first creates a legitimate pre-authentication session, then sends the same session identifier without the optional comma-separated secret. Because path resolution uses only the base session name while encoding requires the suffix, the server opens the real session file but writes the password in plaintext. A password such as x\r\nhasroot=1\r\ntfa_verified=1 therefore creates arbitrary top-level session fields...

🤖 Agent Actions

Updated src/pentesting-web/crlf-0d-0a.md with:

• Optional-secret encoding downgrade technique.
• CRLF session-record injection workflow.
• Raw-store/JSON-cache parser desynchronization and cache promotion.
• Authentication timestamp short-circuit analysis.
• Technical detection and hardening guidance.
• Links to login bypass and cache poisoning/deception pages.
• Reordered references to credit the primary watchTowr research first.

Validation passed with git diff --check; internal links exist and forbidden sources were not used. mdbook was unavailable locally, so a full build was skipped.

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This PR was automatically created by the HackTricks Feed Bot. Please review the changes carefully before merging.

[carlospolop]

🔗 Additional Context

Original Blog Post: https://labs.watchtowr.com/the-internet-is-falling-down-falling-down-falling-down-cpanel-whm-authentication-bypass-cve-2026-41940

Content Categories: Based on the analysis, this content was categorized under "Network Services Pentesting → 80,443 - Pentesting Web → Login Bypass, with cross-references to CRLF Injection and Cache Poisoning and Cache Deception".

Repository Maintenance:

• MD Files Formatting: 1031 files processed

Review Notes:

• This content was automatically processed and may require human review for accuracy
• Check that the placement within the repository structure is appropriate
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Bot Version: HackTricks News Bot v1.0