# What is CVE-2020-0878? > CVE-2020-0878 is a medium-severity flaw (CVSS 4.2) in Internet Explorer from Microsoft, published on 11 September 2020. It is on the list of flaws known to be exploited, so criminals are already using it. The latest forecast puts its chance of use in the next 30 days at 2.7%. If you run an affected version, patch it first. Canonical page: https://www.precursorintelligence.com/what-is/cve-2020-0878 ## At a glance - **Verdict:** Fix this now. Attackers are using this flaw today. If you run an affected version, it goes to the top of your list. - **Precursor Intelligence risk score:** 74 out of 100 (High); action: Emergency patch. Kept up to date as the evidence changes. - **Severity:** Medium (CVSS 4.2 out of 10) - **Known to be exploited:** Yes, it is on the government list of flaws known to be exploited - **Chance of use in the next 30 days:** 2.7% (latest exploit-likelihood forecast) - **Published:** 11 September 2020 - **Record last updated:** 13 March 2025 - **Main product:** Internet Explorer from Microsoft - **Affected products:** 19 ## What is CVE-2020-0878? In plain terms It can be attacked from anywhere on the internet without logging in, but a person has to take an action first. If it works, the attacker can read some data and change some data. ### The official description A remote code execution vulnerability exists in the way that Microsoft browsers access objects in memory. The vulnerability could corrupt memory in a way that could allow an attacker to execute arbitrary code in the context of the current user. An attacker who successfully exploited the vulnerability could gain the same user rights as the current user. If the current user is logged on with administrative user rights, the attacker could take control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. An attacker could host a specially crafted website that is designed to exploit the vulnerability through Microsoft browsers, and then convince a user to view the website. The attacker could also take advantage of compromised websites, or websites that accept or host user-provided content or advertisements, by adding specially crafted content that could exploit the vulnerability. In all cases, however, an attacker would have no way to force users to view the attacker-controlled content. Instead, an attacker would have to convince users to take action, typically via an enticement in email or instant message, or by getting them to open an email attachment. The security update addresses the vulnerability by modifying how Microsoft browsers handle objects in memory. ### What kind of flaw is it? - CWE-787: Out-of-bounds Write ### How an attack on it works - Where an attacker can be: Anywhere on the internet - How hard it is to pull off: Hard: conditions must line up - Login needed first: No login needed - Does someone have to click: Yes, a person has to take an action - What an attacker gets: Can read some data and change some data Severity vector: `CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N` ## Is CVE-2020-0878 being exploited? Yes Attackers are already using it. It is on the government list of flaws known to be exploited, and the latest forecast puts the chance of it being used in the next 30 days at 2.7%. Exploit likelihood over the last 7 days: 2.7%, 2.7%, 2.7%, 2.7%, 2.7%, 2.7%, 2.7%. ### Timeline - 11 September 2020: Published - 13 March 2025: Record last updated - 31 October 2025: Exploit likelihood fell ### How Precursor Intelligence ranks it CVE-2020-0878 scores **74 out of 100 (High)**, with the action "Emergency patch". 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: smaller factor - Threat activity around it: smaller factor 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-2020-0878? The published record lists 19 products. - [Internet Explorer](https://www.precursorintelligence.com/product/microsoft/internet_explorer) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Application): 9, 11 - [Chakracore](https://www.precursorintelligence.com/product/microsoft/chakracore) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Application): version not specified - [Edge](https://www.precursorintelligence.com/product/microsoft/edge) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Application): version not specified - [Windows 10](https://www.precursorintelligence.com/product/microsoft/windows_10) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): 1909 - [Windows 10 1507](https://www.precursorintelligence.com/product/microsoft/windows_10_1507) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified - [Windows 10 1607](https://www.precursorintelligence.com/product/microsoft/windows_10_1607) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified - [Windows 10 1709](https://www.precursorintelligence.com/product/microsoft/windows_10_1709) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified - [Windows 10 1803](https://www.precursorintelligence.com/product/microsoft/windows_10_1803) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified - [Windows 10 1809](https://www.precursorintelligence.com/product/microsoft/windows_10_1809) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified - [Windows 10 1903](https://www.precursorintelligence.com/product/microsoft/windows_10_1903) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified - [Windows 10 1909](https://www.precursorintelligence.com/product/microsoft/windows_10_1909) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified - [Windows 10 2004](https://www.precursorintelligence.com/product/microsoft/windows_10_2004) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified - [Windows 7](https://www.precursorintelligence.com/product/microsoft/windows_7) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified - [Windows 8.1](https://www.precursorintelligence.com/product/microsoft/windows_8.1) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified - [Windows Rt 8.1](https://www.precursorintelligence.com/product/microsoft/windows_rt_8.1) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified - [Windows Server 2008](https://www.precursorintelligence.com/product/microsoft/windows_server_2008) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): r2-sp1 - [Windows Server 2012](https://www.precursorintelligence.com/product/microsoft/windows_server_2012) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): r2 - [Windows Server 2016](https://www.precursorintelligence.com/product/microsoft/windows_server_2016) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified - [Windows Server 2019](https://www.precursorintelligence.com/product/microsoft/windows_server_2019) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): version not specified ## How do I fix CVE-2020-0878? 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 update named in the vendor’s advisory. We’ve put the advisory first in the list. 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. **Check it wasn’t used before you patched.** Because criminals are already using this flaw, look for signs of a break-in on affected systems using the vendor’s guidance. ### References - [portal.msrc.microsoft.com](https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0878) (Patch, Vendor advisory) ## Questions ### What is CVE-2020-0878? CVE-2020-0878 is a medium-severity flaw in Internet Explorer from Microsoft, published on 11 September 2020. It can be attacked from anywhere on the internet without logging in, but a person has to take an action first. If it works, the attacker can read some data and change some data. ### How serious is CVE-2020-0878? It scores 4.2 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2020-0878 is 74 out of 100, which is High. Its action is "Emergency patch". Attackers are using this flaw today. If you run an affected version, it goes to the top of your list. ### Is CVE-2020-0878 being exploited? Attackers are already using it. It is on the government list of flaws known to be exploited, and the latest forecast puts the chance of it being used in the next 30 days at 2.7%. ### Which versions does CVE-2020-0878 affect? For Internet Explorer from Microsoft: 9, 11. The record lists 19 products in all, each with its versions, under "Who is affected" on this page. ### How do I fix CVE-2020-0878? Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet. Because criminals are already using it, also check affected systems for signs of a break-in. ## Does CVE-2020-0878 affect you? Precursor Intelligence keeps checking for you: - **Tell us what you run.** Pick your software from a list, or let us work it out from your website. - **We match it to every flaw.** Over 400,000 published flaws, checked against your list. - **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it. - **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools. Start free (no card, nothing to install): https://www.precursorintelligence.com/register Book a demo: https://www.precursorintelligence.com/contact