This Week in Security

238 Articles

This Week In Security: Zimbra, DNS Poisoning, And Perfctl

October 4, 2024 by 6 Comments

Up first this week is a warning for the few of us still brave enough to host our own email servers. If you’re running Zimbra, it’s time to update, because CVE-2024-45519 is now being exploited in the wild.

That vulnerability is a pretty nasty one, though thankfully requires a specific change from default settings to be exposed. The problem is in postjournal. This logging option is off by default, but when it’s turned on, it logs incoming emails. One of the fields on an incoming SMTP mail object is the RCPT TO: field, with the recipients made of the to, cc, and bcc fields. When postjournal logs this field, it does so by passing it as a bash argument. That execution wasn’t properly sanitized, and wasn’t using a safe call like execvp(). So, it was possible to inject commands using the $() construction.

The details of the attack are known, and researchers are seeing early exploratory attempts to exploit this vulnerability. At least one of these campaigns is attempting to install webshells, so at least some of those attempts have teeth. The attack seems to be less reliable when coming from outside of the trusted network, which is nice, but not something to rely on.

New Tool Corner

What is that binary doing on your system? Even if you don’t do any security research, that’s a question you may ask yourself from time to time. A potential answer is WhoYouCalling. The wrinkle here is that WYC uses the Windows Event Tracing mechanism to collect the network traffic strictly from the application in question. So it’s a Windows only application for now. What you get is a packet capture from a specific executable and all of its children processes, with automated DNS capture to go along. Continue reading “This Week In Security: Zimbra, DNS Poisoning, And Perfctl” →

This Week In Security: Password Sanity, Tank Hacking, And The Mystery 9.9

September 27, 2024 by 15 Comments

It looks like there’s finally hope for sane password policies. The US National Institue of Standards and Technology, NIST, has released a draft of SP 800-63-4, the Digital Identity Guideline.

There’s password guidance in there, like “SHALL NOT impose other composition rules (e.g., requiring mixtures of different character types) for passwords” and “SHALL NOT require users to change passwords periodically.” NIST approved passwords must be at least 8 characters long, with a weaker recommendation of at least 15 characters. Security questions like name of first pet get the axe. And it’s strongly recommended that all ASCII and Unicode characters should be acceptable for passwords.

This is definitely moving in the right direction. NIST guidelines are only binding for government services and contractors, though they do eventually get picked up by banks and other industries. So there’s hope for sane password policies eventually.

Tank Hacking

Researchers at Bitsight are interested in infrastructure security, and they opted to take a closer look at Automatic Tank Gauging (ATG) systems. Those are found at gas stations, as well as any other facility that needs automated monitoring of liquids or gasses in a tank. There is an actual ATG message format, originally designed for RS-232 serial, and woefully unprepared for the interconnected present. The protocol allows for an optional security code, but it maxes out at only six alpha-numeric characters.

Among the vulnerabilities getting announced today, we have a pair of CVSS 10 command injection flaws, a quartet of 9.8 authentication bypass flaws, with one of those being a hardcoded credential — AKA a backdoor. The other CVSS9+ flaw is a SQL injection, with a trio of slightly less serious flaws. Continue reading “This Week In Security: Password Sanity, Tank Hacking, And The Mystery 9.9” →

This Week In Security: Open Source C2, Raptor Trains, And End To End Encryption

September 20, 2024 by 14 Comments

Open Source has sort of eaten everything in software these days. And that includes malware, apparently, with open source Command and Control (C2) frameworks like Sliver and Havoc gaining traction. And of course, this oddball intersection of Open Source and security has intrigued at least one security researcher who has found some interesting vulnerabilities.

Before we dive into what was found, you may wonder why open source malware tools exist. First off, trustworthy C2 servers are quite useful for researchers, who need access to such tools for testing. Then there is Red Teaming, where a security professional launches a mock attack against a target to test its defenses. A C2 is often useful for education and hobby level work, and then there are the true criminals that do use these Open Source tools. It takes all types.

A C2 system consists of an agent installed on compromised systems, usually aiming for stealth. These agents connect to a central server, sending information and then executing any instructions given. And finally there’s a client, which is often just a web interface or even a command line interface.

Now what sort of fun is possible in these C2 systems? Up first is Sliver, written in Go, with a retro command line interface. Sliver supports launching Metasploit on compromised hosts. Turns out, it accidentally supported running Metasploit modules against the server’s OS itself, leading to an easy remote shell from an authenticated controller account.

Havoc has a fancy user interface for the clients, and also a command injection flaw. A service name field gets used to generate a shell command, so you’re only a simple escape away from running commands. That’s not quite as useful as the API that failed open when a bad username/password was given. Oops. Continue reading “This Week In Security: Open Source C2, Raptor Trains, And End To End Encryption” →

This Week In Security: Malicious Rollback, WHOIS, And More

September 13, 2024 by 4 Comments

It’s time to talk about Microsoft’s patch Tuesday, and the odd vulnerability rollback that happened. CVE-2024-43491 has caught some attention, as it’s a 9.8 on the CVSS scale, is under active exploitation, and results in Remote Code Execution (RCE). Yikes, it sounds terrible!

First off, what actually happened? The official statement is that “build version numbers crossed into a range that triggered a code defect”. We don’t know the exact details, but it’s something like an unsigned integer that was interpreted as a signed integer. A build number could have rolled over 32767, and what was intended to be 32768 or higher suddenly became −32767. Lots of “if greater than or equal” logic breaks down in that situation. Because of a logic flaw like this, certain versions of Windows 10 were unintentionally opting out of some historical security fixes.

And that’s where the high CVSS score and active exploitation descriptor comes from. This is simply the highest score of the resurgent flaws, and an acknowledgement that they have been exploited in the past. The good news is that this only applies to Windows 10 build 1507, so either the original install without any of the major updates installed, or one of the Windows 10 Enterprise Long-Term Servicing Branch (LTSB) versions. It seems that the March 2024 monthly security update introduced the problem, and it wasn’t fixed until this month’s updates. Continue reading “This Week In Security: Malicious Rollback, WHOIS, And More” →

This Week In Security: EUCLEAK, Revival Hijack, And More

September 6, 2024 by 5 Comments

[Thomas Roche] of NinjaLab is out with EUCLEAK, (pdf) a physical attack against Infineon security microcontrollers, and the security tokens that contain them. The name is a portmanteau of Euclidean and leak. And no surprise, it’s a data leak in some implementations of the Extended Euclidean Algorithm (EEA), a component of an Elliptical Curve Digital Signature Algorithm (ECDSA).

OK, time to step back. Infineon microcontrollers are the digital smart parts inside popular security tokens like the Yubikey 5, some Java smart cards, and even the Infineon TPMs. These devices all serve a similar purpose. They store one or more secret keys, and are guaranteed to never disclose those keys. Instead, they use their secret keys to do cryptographic functions, like ECDSA signatures, and output the result. There’s even a special set of tests, the Common Criteria, that are intended to backstop these guarantees. What’s interesting is that an otherwise excellent product like the Yubikey 5, that passes all these auditing and certification processes, is still vulnerable.

The actual attack is to perform ECDSA signatures while monitoring the physical chip with an electromagnetic probe. This tiny directional antenna can pick up on EM noise generated by the microprocessor. That EM noise leaks timing information about the internal state of the cryptography, and the secret key can be derived as a result.

This process does require physical access to the token for several minutes. To get useful readings, the plastic case around the security token does need to be disassembled to get the probe close enough to pick up signals. From there it’s at least an hour of post-processing to actually get the key. And most of these security tokens intentionally make the disassembly process rather difficult. The point isn’t that it’s impossible to open up, but that it’s impossible not to notice that your token has been tampered with. Continue reading “This Week In Security: EUCLEAK, Revival Hijack, And More” →

This Week In Security: The Rest Of The IPv6 Story, CVE Hunting, And Hacking The TSA

August 30, 2024 by 2 Comments

We finally have some answers about the Windows IPv6 vulnerability — and a Proof of Concept! The patch was a single change in the Windows TCP/IP driver’s Ipv6pProcessOptions(), now calling IppSendError() instead of IppSendErrorList(). That’s not very helpful on its own, which is why [Marcus Hutchins]’s analysis is so helpful here. And it’s not an easy task, since decompiling source code like this doesn’t give us variable names.

The first question that needs answered is what is the list in question? This code is handling the option field in incoming IPv6 packets. The object being manipulated is a linked list of packet structs. And that linked list is almost always a single member list. When calling IppSendErrorList() on a list with a single member, it’s functionally equivalent to the IppSendError() in the fixed code. The flaw must be in the handling of this list with multiple members. The only way to achieve that criteria is to send a lot of traffic at the machine in question, so it can’t quite keep up with processing packets one at a time. To handle the high throughput, Windows will assemble incoming packets into a linked list and process them in batch.

So what’s next? IppSendErrorList(), takes a boolean and passes it on to each call of IppSendError(). We don’t know what Microsoft’s variable name is, but [Marcus] is calling it always_send_icmp, because setting it to true means that each packet processed will generate an ICMP packet. The important detail is that IppSendError() can have side effects. There is a codepath where the packet gets reverted, and the processing pointer is set back to the beginning of the packet. That’s fine for the first packet in the list, but because the function processes errors on the entire list of packets, the state of the rest of those packets is now much different from what is expected.

This unexpected but of weirdness can be further abused through IPv6 packet fragmentation. With a bit of careful setup, the reversion can cause a length counter to underflow, resulting in data structure corruption, and finally jumping code execution into the packet data. That’s the Remote Code Execution (RCE). And the good news, beyond the IPv6-only nature of the flaw, is that so far it’s been difficult to actually pull the attack off, as it relies on this somewhat non-deterministic “packet coalescing” technique to trigger the flaw.

Continue reading “This Week In Security: The Rest Of The IPv6 Story, CVE Hunting, And Hacking The TSA” →

This Week In Security: Crash Your IPhone, Hack Your Site, And Bluetooth Woes

August 23, 2024 by 6 Comments

There have been some hilarious issues on mobile devices over the years. The HTC Dream had a hidden shell that was discovered when a phone rebooted after sending a text containing just the word “reboot”. iOS has gotten in on the fun from time to time, and this time it’s ""::. Type the double quotes, a colon, and any other character, and Apple’s Springboard service crashes.

Another hacker dug in a bit, and realized that Springboard is trying to jump execution to a null pointer, leading to a crash. It’s very odd that user input breaks the query parser badly enough to jump to null like that. There are a couple interesting questions that we have to ask. Given that the crash trigger is quite flexible, "anything goes":x, is it possible to manipulate that function pointer to be something other than null? And perhaps more importantly, why is the code crashing, instead of an invalid address error as one would expect from a Pointer Authentication Code (PAC) violation? Regardless, the bug seems to be fixed in the latest iOS 18 builds.

Continue reading “This Week In Security: Crash Your IPhone, Hack Your Site, And Bluetooth Woes” →