CVE-2026-63091
MediumCVSS 6.5Exploitation Probability (EPSS)
Low risk22th percentile - higher than 22% of all known CVEs
Summary
ProFTPD before 1.3.9c and 1.3.10rc3 has a signed integer overflow in the mod_sftp SCP size-record parser. Authenticated low-privilege attackers can bypass ASLR by sending UINT64_MAX, causing a negative off_t value. Exploitation leads to reading beyond SSH channel data and writing overread process memory into the uploaded file, disclosing libc, libcrypto, and PIE pointers.
Risk Assessment
The risk involves bypassing ASLR and enabling further memory corruption exploits, potentially leading to full compromise of the ProFTPD server.
Recommendation
Immediately upgrade ProFTPD to version 1.3.9c or later and restrict SFTP access to trusted users.
Other vulnerabilities in ProFTPD
See all- CVE-2015-3306High
The mod_copy module in ProFTPD 1.3.5 allows remote attackers to read and write to arbitrary files via the site cpfr and site cpto commands.
- CVE-2026-42167High
A vulnerability in the mod_sql module of ProFTPD before 1.3.9a allows remote attackers to execute arbitrary code via a username, when USER requests are logged with expansions like %U and the SQL backend allows commands (e.g., COPY TO PROGRAM).
- CVE-2010-20103Critical
A malicious backdoor was embedded in the official ProFTPD 1.3.3c source tarball distributed between November 28 and December 2, 2010. The backdoor implements a hidden FTP command trigger that allows remote, unauthenticated attackers to execute arbitrary shell commands with root privileges.
- CVE-2026-63090High
ProFTPD before versions 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.
- CVE-2026-53994High
Heap buffer overflow in ProFTPD mod_sftp. An authenticated SFTP user can send a packet with length 0, causing an underflow and buffer overflow, leading to session crash or potentially further consequences.
- CVE-2026-35025High
A vulnerability in ProFTPD up to versions 1.3.9b and 1.3.10rc2 allows authenticated FTP users to bypass Directory ACL restrictions by prefixing paths with /proc/self/root in the RNFR command handler. Attackers can exploit unresolved symlink components in dir_canonical_path() to cause dir_check() to perform lexical path comparisons that match no configured Directory block, enabling rename operations on files in DenyAll-protected directories and subsequent retrieval.
- CVE-2026-44331High
In ProFTPD up to version 1.3.9a before commit 7666224, a SQL injection vulnerability exists in sqltab_fetch_clients_cb() in contrib/mod_wrap2_sql.c. When UseReverseDNS is enabled, an attacker can supply a crafted domain name that is passed unsanitized into SQL queries, allowing remote injection of arbitrary SQL commands.
Original NVD description (English source)
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.