# What is CVE-2020-16947? > CVE-2020-16947 is a high-severity flaw (CVSS 7.5) in Outlook from Microsoft, published on 16 October 2020. 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 34%. If you run an affected version, plan in the vendor’s fix. Canonical page: https://www.precursorintelligence.com/what-is/cve-2020-16947 ## At a glance - **Verdict:** Fix this soon. Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month. - **Precursor Intelligence risk score:** 55 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes. - **Severity:** High (CVSS 7.5 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:** 34% (latest exploit-likelihood forecast) - **Published:** 16 October 2020 - **Record last updated:** 31 December 2023 - **Main product:** Outlook from Microsoft - **Affected products:** 3 ## What is CVE-2020-16947? 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 data, change data and take it offline. ### The official description A remote code execution vulnerability exists in Microsoft Outlook software when the software fails to properly handle objects in memory. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the targeted user. If the targeted user is logged on with administrative user rights, an attacker could take control of the affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. Exploitation of the vulnerability requires that a user open a specially crafted file with an affected version of Microsoft Outlook software. In an email attack scenario, an attacker could exploit the vulnerability by sending the specially crafted file to the user and convincing the user to open the file. In a web-based attack scenario, an attacker could host a website (or leverage a compromised website that accepts or hosts user-provided content) that contains a specially crafted file designed to exploit the vulnerability. An attacker would have no way to force users to visit the website. Instead, an attacker would have to convince users to click a link, typically by way of an enticement in an email or instant message, and then convince them to open the specially crafted file. Note that where severity is indicated as Critical in the Affected Products table, the Preview Pane is an attack vector. The security update addresses the vulnerability by correcting how Outlook handles objects in memory. ### What kind of flaw is it? - CWE-125: Out-of-bounds Read - 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 data, change data and take it offline Severity vector: `CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H` ## Is CVE-2020-16947 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 34%. That can change at any time, which is why we keep watching. Exploit likelihood over the last 7 days: 34%, 34%, 34%, 34%, 34%, 34%, 34%. ### Timeline - 16 October 2020: Published - 31 December 2023: Record last updated - 16 June 2026: Exploit likelihood fell ### How Precursor Intelligence ranks it CVE-2020-16947 scores **55 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: 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-2020-16947? The published record lists 3 products. - [Outlook](https://www.precursorintelligence.com/product/microsoft/outlook) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Application): 2016 - [365 Apps](https://www.precursorintelligence.com/product/microsoft/365_apps) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Application): version not specified - [Office](https://www.precursorintelligence.com/product/microsoft/office) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Application): 2019 ## How do I fix CVE-2020-16947? 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. **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 - [portal.msrc.microsoft.com](https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-16947) (Patch, Vendor advisory) - [packetstormsecurity.com](http://packetstormsecurity.com/files/169961/Microsoft-Outlook-2019-16.0.13231.20262-Remote-Code-Execution.html) (Third-party advisory, Vulnerability database) - [zerodayinitiative.com](https://www.zerodayinitiative.com/advisories/ZDI-20-1249/) (Third-party advisory, Vulnerability database) - [zerodayinitiative.com](https://www.zerodayinitiative.com/advisories/ZDI-20-1250/) (Third-party advisory, Vulnerability database) ## Questions ### What is CVE-2020-16947? CVE-2020-16947 is a high-severity flaw in Outlook from Microsoft, published on 16 October 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 data, change data and take it offline. ### How serious is CVE-2020-16947? It scores 7.5 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2020-16947 is 55 out of 100, which is Medium. Its action is "Plan remediation". Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month. ### Is CVE-2020-16947 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 34%. That can change at any time, which is why we keep watching. ### Which versions does CVE-2020-16947 affect? For Outlook from Microsoft: 2016. The record lists 3 products in all, each with its versions, under "Who is affected" on this page. ### How do I fix CVE-2020-16947? 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. ## Does CVE-2020-16947 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