What is a POODLE attack, and does it steal data?

Anton P. | October 04, 2022

A POODLE attack intercepts communications between browsers and web servers. It can expose users’ private information like passwords and credit card numbers if successful.

To capture these details, attackers force browsers to fall back to SSL 3.0 from other, more secure protocols like TLS. The Internet Engineering Task Force (IETF) deprecated SSL versions years ago. However, further research revealed that TLS 1.0 and TLS 1.2 versions are also susceptible to protocol downgrade attacks.

What is a POODLE attack, and does it steal data?

Understanding the POODLE attack

POODLE (Padding Oracle on Downgraded Legacy Encryption) attempts to reverse the encryption performed on users’ data. Such sneaky decryption of secret communications is possible due to several vulnerabilities. More specifically, experts associate POODLE attacks with CVE-2014-3566 and CVE-2014-8730.

So, the attacker wants communications to use a block cipher in flawed CBC mode. The latter process has a security vulnerability, which is susceptible to POODLE. Thus, systems supporting SSL 3.0 and a cipher suite using CBC modes can fall victim to this attack.

Three researchers, Thai Duong, Bodo Möller, and Krzysztof Kotowicz from Google Security Team, discovered the POODLE attack. They published their findings in a research paper in 2014. Over the years, similar downgrade-focused attacks have surfaced, like the SSL stripping attack.

How does the POODLE attack work?

The main issue comes from legacy systems that remain backward-compatible with older protocols like SSL 3.0. So, systems could revert back to SSL to resolve performance or functionality problems.

Such fallback for the sake of a smoother experience is a downgrade dance. And unfortunately, hackers could abuse this possible regression and exploit SSL encryption bugs.

Here is a brief overview of how a POODLE attack works:

  1. The client and server negotiate the connection. Both need to support the chosen protocol. Thus, the handshake will first attempt to offer the newest protocol version. If this fails, the same negotiation begins with an older protocol.
  2. If attackers manage to control the connection, they can enforce the SSL connection automatically. However, perpetrators do need to perform particular man-in-the-middle (MitM) attacks to gain a position of power. For instance, such intrusions are easier on free networks in various public locations.
  3. When clients and servers interact with SSL 3.0 protocol, their communications are no longer safe. An RC4 stream cipher could be the one SSL uses. Its main vulnerability is that by sending data over many connections, each transmission leaks more and more details.
  4. SSL could also use block ciphers in CBC mode. Its vulnerable nature comes from the fact that it does not fully verify the integrity of padding before decryption.
  5. So, perpetrators need to implement MitM attacks and run malicious JavaScript to trigger the connection downgrade. Once the connection supports SSL 3.0, the POODLE attack can occur. It exploits encryption and padding vulnerabilities to capture data in its original form.

POODLE attack is dangerous but not easy to implement

A POODLE attack aims to force a website to drop a secure connection via TLS. However, before the attack exploits SSL 3.0 flaws, the perpetrators need to meet the conditions favorable to MitM.

The best environment for POODLE is an unsecured public network. You can find such hotspots in various public locations like airports, parks, or shopping malls.

Overall, it is unlikely that the POODLE attack could occur remotely. Users need to perform dangerous actions or connect to unsecured networks to become possible targets.

What information can a POODLE attack get?

If a POODLE attack manages to find the necessary conditions, it could retrieve anything users submit. That includes login details like usernames, email addresses, and passwords.

The hackers could get their hands on session cookies and authentication tokens. Such theft could facilitate account takeovers or even identity theft. Successful POODLE attacks could even lead to financial losses if perpetrators retrieve financial information.

Measures to stop POODLE attacks

The most straightforward way to stop POODLE attacks is to disable SSL 3.0 on the server and client. However, it could be impractical under certain conditions.

Furthermore, the POODLE attack could compromise newer protocols to a certain degree. One solution had been including TLS_FALLBACK_SCV for mitigating attempts to downgrade security. It preserves the fallback to SSL for legitimate purposes and stops hackers from triggering these downgrades.

Prevent POODLE and similar attacks

Your connection to the internet, websites, applications, and other online services can never be 100% secure. Furthermore, our research calculated a 130% increase in web threats at the end of 2021. Thus, protecting your digital presence is a priority you cannot dismiss, even though many threats exploit seemingly mundane actions.

However, some habits, settings, and decisions do make you more vulnerable. Here are some tips for protecting your internet activities, submitted data, and overall experience.

  • Avoid connecting to unknown networks. Hotspots in public places can make users vulnerable to traffic interception. Thus, they could open doors for MitM, SSL stripping, and POODLE attacks.
  • Do not trust HTTP websites. If sites use HTTP, never reveal login credentials or other personal information through them.
  • Keep your operating system, browser, and other software updated. Use modern solutions and install updates to combat bugs and vulnerabilities. Many digital threats work because people continue using outdated versions.
  • Connect to a VPN. A Virtual Private Network can secure your connection to any network. Thus, if you enable a VPN and connect to public Wi-Fi, your traffic cannot be read by eavesdroppers. Even if sites or networks do not use appropriate encryption, a VPN will.
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Anton P.

Anton P.

Former chef and the head of Atlas VPN blog team. He's an experienced cybersecurity expert with a background of technical content writing.


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