# CVE-2026-63091: proftpd-dfsg: ProFTPD before 1.3.9c and 1.3.10rc3 contains a signed integer overflow vulnerability in the mod_sftp module's SCP siz...

CVE-2026-63091 is fixed in proftpd-dfsg on 1 platform, first by DEBIAN-CVE-2026-63091, released July 21, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-63091
- Priority: Routine
- CVSS: n/a
- EPSS: 0.0053
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 20, 2026

## Description

ProFTPD before 1.3.9c and 1.3.10rc3 contains a signed integer overflow vulnerability in the mod_sftp module's SCP size-record parser that allows authenticated low-privilege attackers to bypass ASLR by sending a crafted file size value of UINT64_MAX, which results in a negative off_t value. Attackers can exploit the subsequent conversion to uint32_t, causing an approximately 4 GB requested read length and forcing the server to read beyond the end of the SSH channel data and write overread process memory into the uploaded file. In tested configurations, the disclosed data contains libc, libcrypto, and PIE pointers sufficient to derive their randomized base addresses, thereby bypassing ASLR and enabling reliable exploitation of memory corruption vulnerabilities in the same process.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | proftpd-dfsg Debian 13.5 (trixie) | 1.3.8.c+dfsg-4+deb13u3 | [DEBIAN-CVE-2026-63091](https://patchblox.com/security/data/fix/linux/debian-cve-2026-63091.md) | Jul 21, 2026 |
| Linux | proftpd-dfsg Debian 14 | 1.3.9c~dfsg-1 | [DEBIAN-CVE-2026-63091](https://patchblox.com/security/data/fix/linux/debian-cve-2026-63091.md) | Jul 21, 2026 |

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Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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