Author: Jonathan Bennett

543 Articles

This Week In Security: WebP, Cavium, Gitlab, And Asahi Lina

September 22, 2023 by 15 Comments

Last week we covered the latest 0-day from NSO group, BLASTPASS. There’s more details about exactly how that works, and a bit of a worrying revelation for Android users. One of the vulnerabilities used was CVE-2023-41064, a buffer overflow in the ImageIO library. The details have not been confirmed, but the timing suggests that this is the same bug as CVE-2023-4863, a Webp 0-day flaw in Chrome that is known to be exploited in the wild.

The problem seems to be an Out Of Bounds write in the BuildHuffmanTable() function of libwebp. And to understand that, we have to understand libwebp does, and what a Huffman Table has to do with it. The first is easy. Webp is Google’s pet image format, potentially replacing JPEG, PNG, and GIF. It supports lossy and lossless compression, and the compression format for lossless images uses Huffman coding among other techniques. And hence, we have a Huffman table, a building block in the image compression and decompression.

What’s particularly fun about this compression technique is that the image includes not just Huffman compressed data, but also a table of statistical data needed for decompression. The table is rather large, so it gets Huffman compressed too. It turns out, there can be multiple layers of this compression format, which makes the vulnerability particularly challenging to reverse-engineer. The vulnerability is when the pre-allocated buffer isn’t big enough to hold one of these decompressed Huffman tables, and it turns out that the way to do that is to make maximum-size tables for the outer layers, and then malform the last one. In this configuration, it can write out of bounds before the final consistency check.

An interesting note is that as one of Google’s C libraries, this is an extensively fuzzed codebase. While fuzzing and code coverage are both great, neither is guaranteed to find vulnerabilities, particularly well hidden ones like this one. And on that note, this vulnerability is present in Android, and the fix is likely going to wait til the October security update. And who knows where else this bug is lurking. Continue reading “This Week In Security: WebP, Cavium, Gitlab, And Asahi Lina” →

This Week In Security: Blastpass, MGM Heist, And Killer Themes

September 15, 2023 by 7 Comments

There’s yet another 0-day exploit chain discovered as part of NSO Group’s Pegasus malware suite. This one is known as BLASTPASS, and it’s a nasty one. There’s no user interaction required, just receiving an iMessage containing a malicious PassKit attachment.

We have two CVEs issued so far. CVE-2023-41064 is a classic buffer overflow in ImageIO, the Apple framework for universal file format read and write. Then CVE-2023-41061 is a problem in the iOS Wallet implementation. Release 16.6.1 of the mobile OS addresses these issues, and updates have rolled out for macOS 11, 12, and 13.

It’s worth noting that Apple’s Lockdown mode does seem to block this particular exploit chain. Citizen Lab suggests that high-risk users of Apple hardware enable Lockdown Mode for that extra measure of security. Continue reading “This Week In Security: Blastpass, MGM Heist, And Killer Themes” →

This Week In Security: LastPass Shoe Drops, Keys Lost, And Train Whistles Attack

September 8, 2023 by 8 Comments

There has been a rash of cryptocurrency thefts targeting some unexpected victims. Over $35 million has been drained from just over 150 individuals, and the list reads like a who’s-who of the least likely to fall for the normal crypto scams. There is a pattern that has been noticed, that almost all of them had a seed phrase stored in LastPass this past November when the entire LastPass database was breached.

The bulletproof security of the LastPass system depends in part on the rate limiting of authenticating with the LastPass web service. Additionally, accounts created before security improvements in 2018 may have had master passwords shorter than 12 characters, and the hash iterations on those accounts may have been set distressingly low. Since attackers have had unrestricted access to the database, they’ve been able to run offline attacks against accounts with very low iterations, and apparently that approach has been successful.

Microsoft’s Signing Key

You may remember a story from a couple months ago, where Microsoft found the Chinese threat group, Storm-0558, forging authentication tokens using a stolen signing key. There was a big open question at that point, as to how exactly an outside group managed to access such a signing key.

This week we finally get the answer. A crash log from 2021 unintentionally included the key, and Microsoft’s automated redaction system didn’t catch it. That crash dump was brought into development systems, and an engineer’s account was later accessed by Storm-0558. That key should not have worked for enterprise accounts, but a bug in a Microsoft key validation allowed the consumer systems key to work for enterprise accounts. Those issues have been fixed, but after quite a wild ride. Continue reading “This Week In Security: LastPass Shoe Drops, Keys Lost, And Train Whistles Attack” →

This Week In Security: Not A Vulnerability, BGP Bug Propogation, And Press Enter To Hack

September 1, 2023 by 6 Comments

Curl was recently notified of a CVE, CVE-2020-19909, rated at a hair-raising 9.8 on the CVSS scale. And PostgreSQL has CVE-2020-21469, clocking in with a 7.5 severity. You may notice something odd about those two vulnerabilities, but I promise the 2020 date is only the tip of the iceberg here.

Let’s start with PostgreSQL. That vulnerability was only present in version 12.2, which released in February of 2020, and was fixed with the 12.3 release in May of that same year. The problem is a stack buffer overflow, which doesn’t seem to enable code execution, but does cause a denial of service situation. To trigger the bug? Repeatedly send the PostgreSQL daemon the SIGHUP signal.

If you’re familiar with Linux signals, that might sound odd. See, the SIGHUP signal technically indicates the end of a user session, but most daemons use it to indicate a restart or reload request. And to send this signal, a user has to have elevated privileges — elevated enough to simply stop the daemon altogether. Put simply, it’s not a security vulnerability, just a minor bug.

And now on to curl — This one is just bizarre. The issue is a integer overflow in the --retry-delay argument, which specifies in seconds how often curl should retry a failing download. The value is multiplied by 1000 to convert to milliseconds, resulting in an overflow for very large values. The result of that overflow? A smaller value for the retry delay.

[Daniel Stenberg] makes the point that this tale is a wonderful demonstration of the brokenness of the CVE system and NVD’s handling of it. And in this case, it’s hard not to see this as negligence. We have to work really hard to construct a theoretical scenario where this bug could actually be exploited. The best I’ve been able to come up with is an online download tool, where the user can specify part of the target name and a timeout. If that tool had a check to ensure that the timeout was large enough to avoid excess traffic, this bug could bypass that check. Should we be assigning CVEs for that sort of convoluted, theoretical attack?

But here’s the thing, that attack scenario should rate something like a CVSS of 4.8 at absolute worst. NVD assigned this a 9.8. There’s no way you can squint at this bug hard enough to legitimately rank it that severe. At the time of writing, the NVD lists this as “UNDERGOING REANALYSIS”.
Continue reading “This Week In Security: Not A Vulnerability, BGP Bug Propogation, And Press Enter To Hack” →

This Week In Security: WinRAR, DNS Disco, And No Silver Bullets

August 25, 2023 by 1 Comment

So what does WinRAR, day trading, and Visual Basic have in common? If you guessed “elaborate malware campaign aimed at investment brokers”, then you win the Internet for the day. This work comes from Group-IB, another cybersecurity company with a research team. They were researching a malware known as DarkMe, and found an attack on WinRAR being used in the wild, using malicious ZIP files being spread on a series of web forums for traders.

Among the interesting tidbits of the story, apparently at least one of those forums locked down the users spreading the malicious files, and they promptly broke into the forum’s back-end and unlocked their accounts. The vulnerability itself is interesting, too. A rigged zip file is created with identically named image file and folder containing a script. The user tries to open the image, but because the zip is malformed, the WinRAR function gets confused and opens the script instead.

Based on a user’s story from one of those forums, it appears that the end goal was to break into the brokers’ trading accounts, and funnel money into attacker accounts. The one documented case only lost $2 worth of dogecoin.

There was one more vulnerability found in WinRAR, an issue when processing malicious recovery volumes. This can lead to code execution due to a memory access error. Both issues were fixed with release 6.23, so if you still have a WinRAR install kicking around, make sure it’s up to date! Continue reading “This Week In Security: WinRAR, DNS Disco, And No Silver Bullets” →

This Week In Security: TunnelCrack, Mutant, And Not Discord

August 18, 2023 by 10 Comments

Up first is a clever attack against VPNs, using some clever DNS and routing tricks. The technique is known as TunnelCrack (PDF), and every VPN tested was vulnerable to one of the two attacks, on at least one supported platform.
Continue reading “This Week In Security: TunnelCrack, Mutant, And Not Discord” →

Thin Client Wysens Up To Become OpenWrt Router

August 14, 2023 by 27 Comments

For some of us, unused hardware lying around just calls to be used. It seems like [Miles Goodhew] heard the call, and wanted to put a Dell Wyse 3040 thin client to use — in this case as a wireless router. It seems simple enough. OpenWrt supports x64_64 targets, and the thin client has 2G of ram and 8G of flash. It should make for a very capable router.

And before you tell us that it’s just another computer, and that installing OpenWrt on a miniature x86 machine isn’t a hack, note that there were some speedbumps along the way. First off, the motherboard has integrated storage, with the not-very-useful ThinLinux installed, and the system BIOS locked down to prevent reinstall. There is a BIOS clear button on the system’s diminutive motherboard. With the BIOS lock out of the way, a real Linux system can be installed on the small 8 GB mmcblk device.

The next issue the the CPU. It’s an Intel Atom x5 z-series. OpenWrt won’t actually boot on that oddball, not-quite- processor, so [Miles] opted to install Fedora and test via virtualization instead. If that statement makes you do a double-take, you’re not alone. The initial explanation sounded like the mobile-centric processor was missing instructions to make OpenWrt run, but virtualization doesn’t add any instructions for a guest to use. It turns out, the problem is a missing serial port that OpenWrt uses as a debugging output by default.

After a custom OpenWrt compile, the device comes up just as you’d expect, and while it would be underpowered as a desktop, OpenWrt runs happily shuffling bits from Ethernet to wireless adapter at respectable speeds. As [Miles] points out, there’s nothing ground-breaking here, but it’s nice to have the details on re-using these machines compiled in one place. And if you too love the idea of putting OpenWrt in places where nobody intended, we’ve got you covered.