# CVE-2017-17821: Memory corruption in n/a

> Remote attackers can cause denial of service or potentially execute code via a buffer overflow in WebKit's FastBitVector implementation.

- **Severity:** Critical 9.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Dec 2017
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2017-17821, GHSA-353g-x49j-hjg7, UBUNTU-CVE-2017-17821

## What is CVE-2017-17821?

CVE-2017-17821 is a critical memory corruption vulnerability in Apple Safari, published on 21 Dec 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

WTF/wtf/FastBitVector.h in WebKit, as distributed in Safari Technology Preview Release 46, allows remote attackers to cause a denial of service (buffer overflow) or possibly have unspecified other impact because it calls the FastBitVectorWordOwner::resizeSlow function (in WTF/wtf/FastBitVector.cpp) for a purpose other than initializing a bitvector size, and resizeSlow mishandles cases where the old array length is greater than the new array length.

Weakness: CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2017-17821?

It affects 1 product.


Products: Apple Safari.

## How do I fix CVE-2017-17821?

Apply the vendor's patch.

## Is CVE-2017-17821 being exploited?

There is no known exploitation of CVE-2017-17821 in the wild and no public exploit code.

## Other vulnerabilities in Apple Safari

- [CVE-2015-5780](https://insights.sbomify.com/CVE-2015-5780/): Security feature bypass in n/a (critical 10.0)
- [CVE-2014-1300](https://insights.sbomify.com/CVE-2014-1300/): Code injection in n/a (critical 10.0)
- [CVE-2014-1303](https://insights.sbomify.com/CVE-2014-1303/): Memory corruption in n/a (critical 10.0)
- [CVE-2010-1120](https://insights.sbomify.com/CVE-2010-1120/): Code injection in n/a (critical 10.0)
- [CVE-2009-0137](https://insights.sbomify.com/CVE-2009-0137/): Cross-site scripting in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-17821 and fix it if it is affected.

What it is: CVE-2017-17821 is a critical memory corruption vulnerability in Apple Safari, published on 21 Dec 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2017-17821 in the wild and no public exploit code.

Affected product: Apple Safari. 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-2017-17821/ (Markdown: https://insights.sbomify.com/CVE-2017-17821/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-17821
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-17821
- OSV: https://osv.dev/vulnerability/CVE-2017-17821

---
From sbomify Insights: https://insights.sbomify.com/CVE-2017-17821/
Summaries are generated and may contain mistakes; the official description above is the record.