# CVE-2023-6992: Memory corruption issues is Cloudflare zlib implementation

> A local attacker can cause denial of service in Cloudflare's zlib library via a crafted file triggering a heap-based buffer overflow during compression.

- **Severity:** Medium 4.0 (`CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Jan 2024
- **Updated:** 6 Sep 2024
- **Also known as:** AZL-43663, AZL-43807, AZL-43870, AZL-43957, AZL-43969, AZL-44517, AZL-44754, AZL-44811, AZL-45174, AZL-45198, CLSA-2024-1716485905, GHSA-vww9-j87r-4cqh

## What is CVE-2023-6992?

CVE-2023-6992 is a medium-severity memory corruption vulnerability in Cloudflare zlib, published on 4 Jan 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Cloudflare version of zlib library was found to be vulnerable to memory corruption issues affecting the deflation algorithm implementation (deflate.c). The issues resulted from improper input validation and heap-based buffer overflow.
A local attacker could exploit the problem during compression using a crafted malicious file potentially leading to denial of service of the software.
Patches: The issue has been patched in commit  8352d10 https://github.com/cloudflare/zlib/commit/8352d108c05db1bdc5ac3bdf834dad641694c13c . The upstream repository is not affected.

Weakness: CWE-787 (Out-of-bounds Write), CWE-20 (Improper Input Validation), CWE-126 (Buffer Over-read), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2023-6992?

It affects 1 product.


Products: Cloudflare Zlib.

## How do I fix CVE-2023-6992?

Apply the vendor's patch.

## Is CVE-2023-6992 being exploited?

There is no known exploitation of CVE-2023-6992 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-6992 and fix it if it is affected.

What it is: CVE-2023-6992 is a medium-severity memory corruption vulnerability in Cloudflare zlib, published on 4 Jan 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-6992 in the wild and no public exploit code.

Affected product: Cloudflare zlib. 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-2023-6992/ (Markdown: https://insights.sbomify.com/CVE-2023-6992/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-6992
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-6992
- OSV: https://osv.dev/vulnerability/CVE-2023-6992

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-6992/
Summaries are generated and may contain mistakes; the official description above is the record.