CVE-2026-63091
ProFTPD mod_sftp Signed Integer Overflow via SCP Size-Record Parser
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.
INFO
Published Date :
July 20, 2026, 3:16 p.m.
Last Modified :
July 20, 2026, 5:18 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | HIGH | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Update ProFTPD to 1.3.9c or later.
- Update ProFTPD to 1.3.10rc3 or later.
- Apply vendor-provided patches for mod_sftp.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-63091.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-63091 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-63091
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-63091 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-63091 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 20, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-63091', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-20T16:32:31.417303Z'} -
New CVE Received by [email protected]
Jul. 20, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://github.com/proftpd/proftpd', 'vendor': 'proftpd', 'product': 'proftpd', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '1.3.9c', 'versionType': 'custom'}, {'status': 'affected', 'version': '1.3.10rc1', 'lessThan': '1.3.10rc3', 'versionType': 'custom'}], 'defaultStatus': 'affected'}] Added 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. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N Added CWE CWE-190 Added CWE CWE-126 Added Reference https://github.com/proftpd/proftpd/blob/master/RELEASE_NOTES Added Reference https://github.com/proftpd/proftpd/commit/b9b7dde1bcd74bc23366484d53856b67b8d6d95e Added Reference https://github.com/proftpd/proftpd/pull/2201 Added Reference https://github.com/proftpd/proftpd/releases/tag/v1.3.10rc3-3 Added Reference https://github.com/proftpd/proftpd/releases/tag/v1.3.9c Added Reference https://www.vulncheck.com/advisories/proftpd-mod-sftp-signed-integer-overflow-via-scp-size-record-parser