CVE-2026-63091

NameCVE-2026-63091
DescriptionProFTPD 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.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
proftpd-dfsg (PTS)bullseye1.3.7a+dfsg-12+deb11u2vulnerable
bullseye (security)1.3.7a+dfsg-12+deb11u5vulnerable
bookworm1.3.8+dfsg-4+deb12u5vulnerable
bookworm (security)1.3.8+dfsg-4+deb12u4vulnerable
trixie1.3.8.c+dfsg-4+deb13u2vulnerable
forky, sid1.3.9c~dfsg-1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
proftpd-dfsgsource(unstable)1.3.9c~dfsg-1

Notes

https://github.com/proftpd/proftpd/pull/2201
Fixed by: https://github.com/proftpd/proftpd/commit/baf4b7929758c72cdb6cf16325fa25f435d23db6 (v1.3.9c)

Search for package or bug name: Reporting problems