# CVE-2026-63090: ProFTPD mod_sftp Heap Buffer Overflow via SFTP Packet Reassembly

> Authenticated attackers can achieve arbitrary code execution and privilege escalation via a heap buffer overflow in ProFTPD's SFTP module.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Jul 2026
- **Updated:** 28 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-63090, GHSA-wxc2-grp8-f55h, UBUNTU-CVE-2026-63090

## What is CVE-2026-63090?

CVE-2026-63090 is a high-severity memory corruption vulnerability in proftpd, published on 20 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

ProFTPD before 1.3.9c and 1.3.10rc3 contains a heap-based buffer overflow vulnerability in the mod_sftp module that allows authenticated low-privilege attackers to achieve arbitrary code execution by sending crafted SFTP packet fragments exceeding the 16 KB reassembly buffer in the fxp.c component. Attackers can supply oversized fragments to trigger an incorrectly conditioned reallocation, corrupt pool freelist metadata, overwrite the root_fs BSS global pointer to reference a fake filesystem struct, and redirect pr_fsio_stat() to system() via a crafted RENAME request.

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-63090?

It affects 1 product.


Products: Proftpd Proftpd.

## How do I fix CVE-2026-63090?

Upgrade to a fixed version.

## Is CVE-2026-63090 being exploited?

There is no known exploitation of CVE-2026-63090 in the wild and no public exploit code.

## Other vulnerabilities in proftpd

- [CVE-2010-4221](https://insights.sbomify.com/CVE-2010-4221/): Memory corruption in n/a (critical 10.0)
- [CVE-2010-20103](https://insights.sbomify.com/CVE-2010-20103/): ProFTPD 1.3.3c Backdoor Command Execution (critical 9.3)
- [CVE-2011-4130](https://insights.sbomify.com/CVE-2011-4130/): Use after free in n/a (critical 9.0)
- [CVE-2026-35025](https://insights.sbomify.com/CVE-2026-35025/): ProFTPD ACL Bypass via /proc/self/root Path Prefix in RNFR (high 8.6)
- [CVE-2026-42167](https://insights.sbomify.com/CVE-2026-42167/): SQL injection in ProFTPD (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63090 and fix it if it is affected.

What it is: CVE-2026-63090 is a high-severity memory corruption vulnerability in proftpd, published on 20 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-63090 in the wild and no public exploit code.

Affected product: proftpd. 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-2026-63090/ (Markdown: https://insights.sbomify.com/CVE-2026-63090/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63090
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63090
- OSV: https://osv.dev/vulnerability/CVE-2026-63090

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63090/
Summaries are generated and may contain mistakes; the official description above is the record.