# What is CVE-2023-43636? > CVE-2023-43636 is a high-severity flaw (CVSS 8.8) in Edge Virtualization Engine from Linuxfoundation, published on 20 September 2023. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 0.1%. If you run an affected version, plan in the vendor’s fix. Canonical page: https://www.precursorintelligence.com/what-is/cve-2023-43636 ## At a glance - **Verdict:** Plan it in. No sign of exploitation and a low forecast. Patch it in your normal update cycle. - **Precursor Intelligence risk score:** 46 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes. - **Severity:** High (CVSS 8.8 out of 10) - **Known to be exploited:** No, not on the list of flaws known to be exploited today - **Chance of use in the next 30 days:** 0.1% (latest exploit-likelihood forecast) - **Published:** 20 September 2023 - **Record last updated:** 28 September 2023 - **Main product:** Edge Virtualization Engine from Linuxfoundation - **Affected products:** 1 ## What is CVE-2023-43636? In plain terms An attacker has to be already on the device with an ordinary user account, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline. ### The official description In EVE OS, the “measured boot” mechanism prevents a compromised device from accessing the encrypted data located in the vault. As per the “measured boot” design, the PCR values calculated at different stages of the boot process will change if any of their respective parts are changed. This includes, among other things, the configuration of the bios, grub, the kernel cmdline, initrd, and more. However, this mechanism does not validate the entire rootfs, so an attacker can edit the filesystem and gain control over the system. As the default filesystem used by EVE OS is squashfs, this is somewhat harder than an ext4, which is easily changeable. This will not stop an attacker, as an attacker can repackage the squashfs with their changes in it and replace the partition altogether. This can also be done directly on the device, as the “003-storage-init” container contains the “mksquashfs” and “unsquashfs” binaries (with the corresponding libs). An attacker can gain full control over the device without changing the PCR values, thus not triggering the “measured boot” mechanism, and having full access to the vault. Note: This issue was partially fixed in these commits (after disclosure to Zededa), where the config partition measurement was added to PCR13: • aa3501d6c57206ced222c33aea15a9169d629141 • 5fef4d92e75838cc78010edaed5247dfbdae1889. This issue was made viable in version 9.0.0 when the calculation was moved to PCR14 but it was not included in the measured boot. ### What kind of flaw is it? - CWE-345: Insufficient Verification of Data Authenticity ### How an attack on it works - Where an attacker can be: Already on the device - How hard it is to pull off: Easy: no special conditions - Login needed first: An ordinary user account - Does someone have to click: No, nobody has to do anything - What an attacker gets: Can read data, change data and take it offline Severity vector: `CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H` ## Is CVE-2023-43636 being exploited? Not that we know of It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 0.1%. That can change at any time, which is why we keep watching. Exploit likelihood over the last 7 days: 0.1%, 0.1%, 0.1%, 0.1%, 0.1%, 0.1%, 0.1%. ### Timeline - 20 September 2023: Published - 28 September 2023: Record last updated ### How Precursor Intelligence ranks it CVE-2023-43636 scores **46 out of 100 (Medium)**, with the action "Plan remediation". Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less: - Evidence it is being exploited: biggest factor - How severe it is: strong factor - How widely exposed it is: key context - Real threat activity around it: key context 85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it. ## Who is affected by CVE-2023-43636? The published record lists 1 product. Versions are as published: "before 8.6.0" means every version up to, but not including, 8.6.0. - [Edge Virtualization Engine](https://www.precursorintelligence.com/product/linuxfoundation/edge_virtualization_engine) by [Linuxfoundation](https://www.precursorintelligence.com/vendors/linuxfoundation) (Operating system): before 8.6.0, 9.0.0 to before 9.5.0 ## How do I fix CVE-2023-43636? 1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list. 2. **Apply the vendor’s fix.** Install the latest update from the vendor. The references list where the vendor has published details. 3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in. 4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood. ### References - [asrg.io](https://asrg.io/security-advisories/cve-2023-43636/) ## Questions ### What is CVE-2023-43636? CVE-2023-43636 is a high-severity flaw in Edge Virtualization Engine from Linuxfoundation, published on 20 September 2023. An attacker has to be already on the device with an ordinary user account, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline. ### How serious is CVE-2023-43636? It scores 8.8 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2023-43636 is 46 out of 100, which is Medium. Its action is "Plan remediation". No sign of exploitation and a low forecast. Patch it in your normal update cycle. ### Is CVE-2023-43636 being exploited? It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 0.1%. That can change at any time, which is why we keep watching. ### Which versions does CVE-2023-43636 affect? For Edge Virtualization Engine from Linuxfoundation: before 8.6.0, 9.0.0 to before 9.5.0. ### How do I fix CVE-2023-43636? Install the update the vendor names in its advisory. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet. ## Does CVE-2023-43636 affect you? 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