Understanding HTTP Cookie Attributes: Security Risks and Bypass Techniques

🔒 All HTTP Cookie Attributes Explained (With Bypass Techniques)

Cookies are used for session management, authentication, tracking, and user preferences in web applications. Secure cookies rely on attributes to protect against attacks like XSS, CSRF, and session hijacking.

Here’s a detailed list of all cookie attributes, their purpose, and how attackers can bypass them. 🚨

🔐 Secure

What It Does?

• Ensures that the cookie is only sent over HTTPS (encrypted connections).
• Prevents transmission over HTTP, reducing the risk of MITM (Man-in-the-Middle) attacks.

Set-Cookie: session=abc123; Secure

⚠️ Bypass Techniques

• Downgrade Attack – If a website allows both HTTP & HTTPS, an attacker can force a victim to visit the HTTP version to steal cookies.
• SSL Stripping Attack – Tools like sslstrip intercept HTTPS → HTTP downgrades, exposing cookies.
• Misconfigured Redirects – If Secure isn’t enforced strictly, the cookie might be leaked via insecure HTTP.

🛡 Mitigation:

• Use HSTS (Strict-Transport-Security) to force HTTPS.
• Redirect HTTP → HTTPS at the server level.

🛑 HttpOnly

What It Does?

• Prevents JavaScript (document.cookie) from accessing the cookie.
• Protects against XSS attacks where scripts try to steal session tokens.

Set-Cookie: auth=xyz789; HttpOnly

⚠️ Bypass Techniques

• Cross-Site Scripting (XSS) via Headers – Attackers can steal session tokens using headers instead of JavaScript, e.g.:

  fetch('/account', {credentials: 'include'})

• Session Fixation – Attackers inject their own cookie and trick users into using a compromised session.
• Cross-Site Script Inclusion (XSSI) – Attackers inject malicious scripts into JSON API responses to extract data.

🛡 Mitigation:

• Prevent XSS (CSP, sanitization, escaping user input).
• Use SameSite and Secure together to limit exposure.

🛡 SameSite (Strict, Lax, None)

What It Does?

• Controls whether cookies are sent with cross-site requests.
• Prevents Cross-Site Request Forgery (CSRF) attacks.

Set-Cookie: csrf=abc123; SameSite=Strict

🚀 Modes & Their Security

• Strict – Blocks cookies for all cross-site requests (best for security). 🔒
• Lax – Allows cookies for top-level navigations (not for embedded content). 🟠
• None – Allows cookies in all cross-site requests (MUST use Secure). 🚨

🌍 Domain

What It Does?

• Defines which subdomains can access the cookie.
• By default, only the exact domain that set the cookie can use it.

Set-Cookie: user=John; Domain=.example.com

📍 Path

What It Does?

• Limits which URLs can access the cookie.

Set-Cookie: session=xyz123; Path=/admin

🕒 Expiration & Max-Age

What It Does?

• Controls how long the cookie is stored.
• Expires: Sets an exact expiration date.
• Max-Age: Sets duration in seconds.

Set-Cookie: session=abc123; Max-Age=3600; Expires=Tue, 15 Mar 2025 12:00:00 GMT

⚡ Priority (High, Medium, Low)

What It Does?

• Determines which cookies are deleted first when browser storage is full.

Set-Cookie: session=xyz123; Priority=High

🛠 Summary of Cookie Attributes & Bypass Techniques

Attribute	Purpose	Bypass Method	Mitigation
Secure	Forces HTTPS-only cookies	SSL Stripping, HTTP Downgrade	HSTS, force HTTPS
HttpOnly	Blocks JS access	Header-based attacks, XSS	XSS prevention
SameSite	Prevents CSRF	Open redirects, XS-Leaks	Use Strict mode
Domain	Controls subdomain access	Subdomain takeover	Avoid Domain unless needed
Path	Limits cookie access	Path traversal	Restrict Path scope
Expiry	Sets cookie lifetime	Session fixation	Use HttpOnly for sessions

🚀 Final Thoughts

🔥 Security Tip: Always use Secure, HttpOnly, and SameSite together for strong security. 🚀