# CVE-2023-3603: Processing sftp server read may cause null dereference

> A missing allocation check in libssh allows a malicious client to cause a null dereference and crash the SFTP server via large read requests.

- **Severity:** Low 3.1 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 21 Jul 2023
- **Updated:** 26 Sep 2024
- **Also known as:** GHSA-2c4f-vgwr-82q6

## What is CVE-2023-3603?

CVE-2023-3603 is a low-severity vulnerability in Fedora Extra Packages for Enterprise Linux 7, published on 21 Jul 2023. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A missing allocation check in sftp server processing read requests may cause a NULL dereference on low-memory conditions. The malicious client can request up to 4GB SFTP reads, causing allocation of up to 4GB buffers, which was not being checked for failure. This will likely crash the authenticated user's sftp server connection (if implemented as forking as recommended). For thread-based servers, this might also cause DoS for legitimate users.

Given this code is not in any released versions, no security releases have been issued.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2023-3603?

It affects 1 product.


Products: Libssh Libssh.

## How do I fix CVE-2023-3603?

No fix has been published for CVE-2023-3603 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-3603 being exploited?

There is no known exploitation of CVE-2023-3603 in the wild and no public exploit code.

## Other vulnerabilities in Fedora Extra Packages for Enterprise Linux 7

- [CVE-2026-59851](https://insights.sbomify.com/CVE-2026-59851/): Libssh: libssh: authentication bypass via missing gssapi principal check (high 8.8)
- [CVE-2025-5987](https://insights.sbomify.com/CVE-2025-5987/): Libssh: invalid return code for chacha20 poly1305 with openssl backend (high 8.1)
- [CVE-2025-14821](https://insights.sbomify.com/CVE-2025-14821/): Libssh: libssh: insecure default configuration leads to local man-in-the-middle attacks on windows (high 7.8)
- [CVE-2012-4560](https://insights.sbomify.com/CVE-2012-4560/): Memory corruption in n/a (high 7.5)
- [CVE-2012-4562](https://insights.sbomify.com/CVE-2012-4562/): Integer overflow in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-3603 and fix it if it is affected.

What it is: CVE-2023-3603 is a low-severity vulnerability in Fedora Extra Packages for Enterprise Linux 7, published on 21 Jul 2023. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-3603 in the wild and no public exploit code.

Affected product: Fedora Extra Packages for Enterprise Linux 7. 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-2023-3603/ (Markdown: https://insights.sbomify.com/CVE-2023-3603/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-3603
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-3603
- OSV: https://osv.dev/vulnerability/CVE-2023-3603

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From sbomify Insights: https://insights.sbomify.com/CVE-2023-3603/
Summaries are generated and may contain mistakes; the official description above is the record.