This Week in Security

246 Articles

This Week In Security: Github, Google, And Realtek

February 3, 2023 by 4 Comments

GitHub Desktop may have stopped working for you yesterday, Febuary 2nd. The reason was an unauthorized access to some decidedly non-public repositories. The most serious bit of information that escaped was code signing certificates, notably used for GitHub Desktop and Atom. Those certificates were password protected, so it’s unlikely they’ve been abused yet. Even so, Github is taking the proper steps of revoking those certificates.

The only active certificate that was revoked was used for signing the Mac releases of GitHub Desktop, so quite a few older versions of that software is no longer easily installed. If nothing else, it’s a reminder that even a project with a well run security team can have problems.

Sh1mmer-ing Chromebooks

There’s a new, clever attack on the Chromebook, specifically with the goal of unenrolling the device from an educational organization. And the “vulnerability” is a documented feature, the RMA Shim. That’s a special boot loader target that contains a valid signature, but allows the booting of other code, intended for troubleshooting and fixing devices in a repair center. Quite a few of those images have leaked, and Sh1mmer combines the appropriate image with a boot menu with some interesting options.

The first is unenrolling, so the device will act like a privately owned computer. This gets rid of content blocks and allows removing extensions. But wait, there’s more. Like rooting the device, a raw Bash terminal, and re-enabling developer mode. Now, as far as we can tell, this doesn’t *directly* break device encryption, but it’s likely that the RMA shim could be abused to tamper with the device’s filesystem. Meaning that the leak of a bunch of signed shims is a big problem for device security. If you use a Chromebook, it might be time to do some research on whether that model’s shim has been leaked. Continue reading “This Week In Security: Github, Google, And Realtek” →

This Week In Security: GTA, Apple And Android, And Insecure Boot

January 27, 2023 by 11 Comments

When we first saw tweets about a security issue in Grand Theft Auto V, it sounded a bit like a troll. “Press ‘alt and f4’ to unlock a cheat mode”, or the hacker that claims to be able to delete your character. [Tez2]’s warning tweet that you shouldn’t play GTA Online without a firewall sounds like another of these online urban legends. But this one actually seems legit. NIST is even in on the fun, assigning CVE-2023-24059 for the exploit.

When playing an online game, other users send a “join request” to join the active session. This packets can contain malformed data which has been observed to crash the game client remotely. It’s believed, though not publicly confirmed, that it’s also a Remote Code Execution (RCE) vulnerability. It seems likely that this aspect will be added to some of the various cheat panels that are already widely used for this 10-year-old game. So now, rather than just giving your own character infinite ammo and health, you can inflict some havoc on other players, possibly up to corrupting their character files and getting them banned.

But why stop there? If we have code execution inside the game, what stops another player from launching a real attack? A video game isn’t sandboxed like a browser, and there’s nothing preventing a disk wiper attack or even a worm from compromising a bunch of players. The worst part is that it’s an old game, and even though there’s a large playerbase, it’s not guaranteed to get a fix. There’s at least one project aiming to be a firewall to prevent the issue. Continue reading “This Week In Security: GTA, Apple And Android, And Insecure Boot” →

This Week In Security: Git Deep Dive, Mailchimp, And SPF

January 20, 2023 by 10 Comments

First up, git has been audited. This was an effort sponsored by the Open Source Technology Improvement Fund (OSTIF), a non-profit working to improve the security of Open Source projects. The audit itself was done by researchers from X41 and GitLab, and two critical vulnerabilities were found, both caused by the same bad coding habit — using an int to hold buffer lengths.

On modern systems, a size_t is always unsigned, and the same bit length as the architecture bit-width. This is the proper data type for string and buffer lengths, as it is guaranteed not to overflow when handling lengths up to the maximum addressable memory on the system. On the other hand, an int is usually four bytes long and signed, with a maximum value of 2^31-1, or 2147483647 — about 2 GB. A big buffer, but not an unheard amount of data. Throw something that large at git, and it will break in unexpected ways.

Our first example is CVE-2022-23521, an out of bounds write caused by an int overflowing to negative. A .gitattributes file can be committed to a repository with a modified git client, and then checking out that repository will cause the num_attrs variable to overflow. Push the overflow all the way around to a small negative number, and git will then vastly under-allocate the attributes buffer, and write all that data past the end of the allocated buffer.

CVE-2022-41903 is another signed integer overflow, this time when a pretty print format gets abused to do something unexpected. Take a look at this block of code:

Continue reading “This Week In Security: Git Deep Dive, Mailchimp, And SPF” →

This Week In Security: Cacti RCE, VMs In The Browser, And SugarCRM

January 13, 2023 by 7 Comments

This week we start with a Remote Code Execution (RCE) vulnerability that has potential to be a real pain for sysadmins. Cacti, the system monitoring and graphing solution, has a pair of bugs that chain together to allow an attacker with unauthenticated access to the HTTP/S port to trivially execute bash commands. The first half of this attack is an authentication bypass, and it’s embarrassingly trivial. The Cacti authentication code trusts the Forwarded-For: header in the request. Set it to the server’s IP, and the authentication code treats it like a localhost request, bypassing any real authentication process.

The second half is found in the remote_agent.php endpoint, where the poller_id is set by the user and treated as a string. Then, if the right host_id and local_data_id item is triggered, that string is concatenated into a proc_open() function call. The string isn’t sanitized, so it’s trivial enough to include a second command to run, dropping a webshell, for instance.

Version 1.2.23 of Cacti contains the fix, and released on the 2nd. This one is likely to be exploited, and if automated exploitation hasn’t started already, it likely will soon. So if you have a Cacti install, go double-check that the interface isn’t exposed to the world.

JSON Web Token

Researchers at Unit 42 found an exploit that can be used to achieve an RCE in the JsonWebToken project. The issue is this library’s verify() function, which takes arguments of the token to check, the key to use, and options. If there aren’t any algorithms specified in the options object, then the key is processed as a PEM string. The toString() method of that key is called during the actual check, and the assumption is that it’s either a string or buffer. But what if the key passed in to the verify() function was actually a complex object, bringing it’s own toString() method along to play. At that point, we have arbitrary code execution. And if this code is running on the server-side under node.js, that means a popped server.

But wait, it’s not that simple, right? It’s not like a valid JWT can contain an arbitrary object — that would be a problem all on its own. So CVE-2022-23529 is a stepping-stone. It’s insecure code, but the rest of the application has to have another vulnerability for this one to be reachable. Continue reading “This Week In Security: Cacti RCE, VMs In The Browser, And SugarCRM” →

This Week In Security: Lastpass Takeaway, Bitcoin Loss, And PyTorch

January 6, 2023 by 10 Comments

We mentioned the LastPass story in closing a couple weeks ago, but details were still a bit scarce. The hope was that LastPass would release more transparent information about what happened, and how many accounts were accessed. Unfortunately it looks like the December 22nd news release is all we’re going to get. For LastPass users, it’s time to make some decisions.

To recap, an attacker used information from the August 2022 breach to target a LastPass Employee with a social engineering ploy. This succeeded, and the attacker managed to access LastPass backups, specifically a customer account database and customer vaults. There has been no official word of how many users’ data were included, but the indication is that it was the entire dataset. And to make matters worse, the encrypted vault is only partially encrypted. Saved URLs were exposed as plain-text to the attacker, though usernames and passwords are still encrypted using your master password.

So what should a LastPass user do now? It depends. We can assume that whoever has the LastPass vault data is currently throwing every password list available at it. If you used a weak password — derived from words in any language or previously compromised — then it’s time to change all of your passwords that were in the vault. They are burned. Continue reading “This Week In Security: Lastpass Takeaway, Bitcoin Loss, And PyTorch” →

This Week In Security: Adblock For Security, ProxyNotShell Lives, And CVSS 10 To Not Worry About

December 30, 2022 by 14 Comments

The ubiquity of ransomware continues, this time with The Guardian announcing they were partially shut down from an attack. Staff are working from home as the incident is being investigated and data is recovered. Publishing seems to be continuing, and the print paper ran as expected.

There have been a couple reports published recently on how ransomware and other malware is distributed, the first being a public service announcement from the FBI, detailing what might be a blindly obvious attack vector — search engine advertising. A bad actor picks a company or common search term, pays for placement on a search engine, and then builds a fake web site that looks legitimate. For bonus points, this uses a typosquatted domain, like adobe[dot]cm or a punycode domain that looks even closer to the real thing.

The FBI has a trio of recommendations, one of which I whole-heartedly agree with. Their first suggestion is to inspect links before clicking them, which is great, except for the punycode attack. In fact, there are enough lookalike glyphs to make this essentially useless. Second is to type in URLs directly rather than using a search engine to find a company’s site. This is great so long as you know the URL and don’t make a typo. But honestly, haven’t we all accidentally ended up at website[dot]co by doing this? Their last recommendation is the good one, and that is to run a high-quality ad-blocker for security. Just remember to selectively disable blocking for websites you want to support. (Like Hackaday!) Continue reading “This Week In Security: Adblock For Security, ProxyNotShell Lives, And CVSS 10 To Not Worry About” →

This Week In Security: GitHub Actions, SHA-1 Retirement, And A Self-Worming Vulnerability

December 23, 2022 by 6 Comments

It should be no surprise that running untrusted code in a GitHub Actions workflow can have unintended consequences. It’s a killer feature, to automatically run through a code test suite whenever a pull request is opened. But that pull request is run in some part of the target’s development environment, and there’s been a few clever attacks found over the years that take advantage of that. There’s now another one, what Legit Security calls Github Environment Injection, and there were some big-name organizations vulnerable to it.

The crux of the issue is the $GITHUB_ENV file, which contains environment variables to be set in the Actions environment. Individual variables get added to this file as part of the automated action, and that process needs to include some sanitization of data. Otherwise, an attacker can send an environment variable that includes a newline and completely unintended environment variable. And an unintended, arbitrary environment variable is game over for the security of the workflow. The example uses the NODE_OPTIONS variable to dump the entire environment to an accessible output. Any API keys or other secrets are revealed.

This particular attack was reported to GitHub, but there isn’t a practical way to fix it architecturally. So it’s up to individual projects to be very careful about writing untrusted data into the $GITHUB_ENV file.

Continue reading “This Week In Security: GitHub Actions, SHA-1 Retirement, And A Self-Worming Vulnerability” →