# CVE-2021-26411: Microsoft Internet Explorer Memory Corruption

> Attackers can exploit a use-after-free flaw in Internet Explorer to execute arbitrary code, requiring users to apply vendor patches.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L/E:P/RL:O/RC:C`)
- **Exploited in the wild:** Yes, since 3 Nov 2021 (CISA KEV), used in ransomware
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 11 Mar 2021
- **Updated:** 1 Oct 2026
- **Also known as:** GHSA-c5rh-mmr6-c7ch

## What is CVE-2021-26411?

CVE-2021-26411 is a high-severity use after free vulnerability in Microsoft Edge, published on 11 Mar 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Internet Explorer Memory Corruption Vulnerability

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-26411?

It affects 2 products.


Products: Microsoft Edge, Microsoft Internet Explorer.

## How do I fix CVE-2021-26411?

No fix has been published for CVE-2021-26411 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 17 Nov 2021.

## Is CVE-2021-26411 being exploited?

Yes. Attackers have exploited CVE-2021-26411 in the wild since at least 3 Nov 2021, including in ransomware campaigns.

Public exploit code:

- https://github.com/CrackerCat/CVE-2021-26411 (github_poc): https://github.com/CrackerCat/CVE-2021-26411

## Other vulnerabilities in Microsoft Edge

- [CVE-2016-7200](https://insights.sbomify.com/CVE-2016-7200/): Microsoft Edge Memory Corruption (high 8.8, exploited in the wild)
- [CVE-2016-7201](https://insights.sbomify.com/CVE-2016-7201/): Microsoft Edge Memory Corruption (high 8.8, exploited in the wild)
- [CVE-2017-0037](https://insights.sbomify.com/CVE-2017-0037/): Microsoft Edge and Internet Explorer Type Confusion (high 8.1, exploited in the wild)
- [CVE-2016-3351](https://insights.sbomify.com/CVE-2016-3351/): Microsoft Internet Explorer and Edge Information Disclosure (medium 6.5, exploited in the wild)
- [CVE-2017-0028](https://insights.sbomify.com/CVE-2017-0028/): Memory corruption in Microsoft ChakraCore (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-26411 and fix it if it is affected.

What it is: CVE-2021-26411 is a high-severity use after free vulnerability in Microsoft Edge, published on 11 Mar 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: Yes. Attackers have exploited CVE-2021-26411 in the wild since at least 3 Nov 2021, including in ransomware campaigns.

Affected product: Microsoft Edge. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-26411/ (Markdown: https://insights.sbomify.com/CVE-2021-26411/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-26411
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-26411
- OSV: https://osv.dev/vulnerability/CVE-2021-26411

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-26411/
Summaries are generated and may contain mistakes; the official description above is the record.