VulnerabilityAnalyzed

CVE-2026-63091

HIGH 7.1EPSS 0.53%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.53%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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.

CVSS 4.0: 7.1 HIGHCVSS:4.0/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/M
EPSS: 0.53% probability · 43th percentile
CISA KEV: Not listed
Weakness: CWE-126, CWE-190
Affected: proftpd/proftpd
Source: disclosure@vulncheck.com

References

https://github.com/proftpd/proftpd/blob/master/RELEASE_NOTESRelease Notes
https://github.com/proftpd/proftpd/commit/b9b7dde1bcd74bc23366484d53856b67b8d6d95ePatch
https://github.com/proftpd/proftpd/pull/2201Issue Tracking, Patch
https://github.com/proftpd/proftpd/releases/tag/v1.3.10rc3-3Product, Release Notes
https://github.com/proftpd/proftpd/releases/tag/v1.3.9cProduct, Release Notes
https://www.vulncheck.com/advisories/proftpd-mod-sftp-signed-integer-overflow-via-scp-size-record-parserPatch, Release Notes, Third Party Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.