UnratedFix available

DEBIAN-CVE-2026-53994

Type: advisorySource: OSV1 source record

ProFTPD mod_sftp contains a heap-based buffer overflow reachable by an authenticated SFTP user. The fxp_packet_read() function accepts the attacker-supplied 32-bit big-endian SFTP packet length without a minimum sanity check. A value of 0 causes an unsigned subtraction elsewhere in the read path to underflow to approximately 4 GB. That oversized request reaches the core memory allocator, where the rounded size is computed in size_t but passed to new_block() as a 32-bit int; the low 32 bits of 0x100000000 are 0, so new_block() returns a small (~512-byte) block while the caller is told it received ~4 GB. The subsequent fill loop then streams attacker-controlled bytes past the end of the 544-byte allocation, producing an attacker-controlled heap buffer overflow. An authenticated user can crash the per-connection ProFTPD session child on demand with a single malformed SFTP packet (packet_len=0 followed by a body greater than approximately 544 bytes), producing reliable authenticated remote denial of service. Depending on heap layout and adjacent allocations, heap metadata corruption and further consequences beyond denial of service may be possible, though only denial of service is demonstrated by the supplied proof of concept.

Announced 18 Jul 2026Group revision 1

Original source ↗

DEBIAN-CVE-2026-53994

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: osv:DEBIAN-CVE-2026-53994

proftpd-dfsg

Source reference: /affected/0/package/name

Affected versions: 1.3.8+dfsg-4
Source reference: /affected/0/versions
1.3.8+dfsg-4+deb12u1
Source reference: /affected/0/versions
1.3.8+dfsg-4+deb12u2
Source reference: /affected/0/versions
1.3.8+dfsg-4+deb12u3
Source reference: /affected/0/versions
1.3.8+dfsg-4+deb12u4
Source reference: /affected/0/versions
1.3.8+dfsg-4+deb12u5
Source reference: /affected/0/versions
1.3.8+dfsg-5
Source reference: /affected/0/versions
1.3.8+dfsg-6
Source reference: /affected/0/versions
1.3.8+dfsg-7
Source reference: /affected/0/versions
1.3.8+dfsg-8
Source reference: /affected/0/versions
1.3.8.a+dfsg-1
Source reference: /affected/0/versions
1.3.8.b+dfsg-1
Source reference: /affected/0/versions
1.3.8.b+dfsg-2
Source reference: /affected/0/versions
1.3.8.b+dfsg-3
Source reference: /affected/0/versions
1.3.8.b+dfsg-4
Source reference: /affected/0/versions
1.3.8.c+dfsg-1
Source reference: /affected/0/versions
1.3.8.c+dfsg-2
Source reference: /affected/0/versions
1.3.8.c+dfsg-3
Source reference: /affected/0/versions
1.3.8.c+dfsg-4
Source reference: /affected/0/versions
1.3.9a~dfsg-1
Source reference: /affected/0/versions
1.3.9b~dfsg-1
Source reference: /affected/0/versions
1.3.9c~dfsg-1
Source reference: /affected/0/versions
1.3.9d~dfsg-1
Source reference: /affected/0/versions
1.3.9~dfsg-1
Source reference: /affected/0/versions
1.3.9~dfsg-2
Source reference: /affected/0/versions
1.3.9~dfsg-3
Source reference: /affected/0/versions
1.3.9~dfsg-4
Source reference: /affected/0/versions
1.3.9~dfsg-5
Source reference: /affected/0/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

proftpd-dfsg

Source reference: /affected/1/package/name

Affected versions: 1.3.8.c+dfsg-4
Source reference: /affected/1/versions
1.3.8.c+dfsg-4+deb13u1
Source reference: /affected/1/versions
1.3.8.c+dfsg-4+deb13u2
Source reference: /affected/1/versions
Fixed versions: 1.3.8.c+dfsg-4+deb13u3
Source reference: /affected/1/ranges
Prerequisites: Not stated in this record

proftpd-dfsg

Source reference: /affected/2/package/name

Affected versions: 1.3.8.c+dfsg-4
Source reference: /affected/2/versions
1.3.9a~dfsg-1
Source reference: /affected/2/versions
1.3.9~dfsg-1
Source reference: /affected/2/versions
1.3.9~dfsg-2
Source reference: /affected/2/versions
1.3.9~dfsg-3
Source reference: /affected/2/versions
1.3.9~dfsg-4
Source reference: /affected/2/versions
1.3.9~dfsg-5
Source reference: /affected/2/versions
Fixed versions: 1.3.9b~dfsg-1
Source reference: /affected/2/ranges
Prerequisites: Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          }
        ]
      }
    ],
    "package": {
      "name": "proftpd-dfsg",
      "purl": "pkg:deb/debian/proftpd-dfsg?arch=source&distro=bookworm",
      "ecosystem": "Debian:12"
    },
    "versions": [
      "1.3.8+dfsg-4",
      "1.3.8+dfsg-4+deb12u1",
      "1.3.8+dfsg-4+deb12u2",
      "1.3.8+dfsg-4+deb12u3",
      "1.3.8+dfsg-4+deb12u4",
      "1.3.8+dfsg-4+deb12u5",
      "1.3.8+dfsg-5",
      "1.3.8+dfsg-6",
      "1.3.8+dfsg-7",
      "1.3.8+dfsg-8",
      "1.3.8.a+dfsg-1",
      "1.3.8.b+dfsg-1",
      "1.3.8.b+dfsg-2",
      "1.3.8.b+dfsg-3",
      "1.3.8.b+dfsg-4",
      "1.3.8.c+dfsg-1",
      "1.3.8.c+dfsg-2",
      "1.3.8.c+dfsg-3",
      "1.3.8.c+dfsg-4",
      "1.3.9a~dfsg-1",
      "1.3.9b~dfsg-1",
      "1.3.9c~dfsg-1",
      "1.3.9d~dfsg-1",
      "1.3.9~dfsg-1",
      "1.3.9~dfsg-2",
      "1.3.9~dfsg-3",
      "1.3.9~dfsg-4",
      "1.3.9~dfsg-5"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-53994.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          },
          {
            "fixed": "1.3.8.c+dfsg-4+deb13u3"
          }
        ]
      }
    ],
    "package": {
      "name": "proftpd-dfsg",
      "purl": "pkg:deb/debian/proftpd-dfsg?arch=source&distro=trixie",
      "ecosystem": "Debian:13"
    },
    "versions": [
      "1.3.8.c+dfsg-4",
      "1.3.8.c+dfsg-4+deb13u1",
      "1.3.8.c+dfsg-4+deb13u2"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-53994.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          },
          {
            "fixed": "1.3.9b~dfsg-1"
          }
        ]
      }
    ],
    "package": {
      "name": "proftpd-dfsg",
      "purl": "pkg:deb/debian/proftpd-dfsg?arch=source&distro=forky",
      "ecosystem": "Debian:14"
    },
    "versions": [
      "1.3.8.c+dfsg-4",
      "1.3.9a~dfsg-1",
      "1.3.9~dfsg-1",
      "1.3.9~dfsg-2",
      "1.3.9~dfsg-3",
      "1.3.9~dfsg-4",
      "1.3.9~dfsg-5"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-53994.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  }
]

Publisher severity

No explicit severity was provided.

Event: #57793 · Revision 1
Added to Heist Feed: Sun, 25 Oct 2026 17:30:25 GMT
Publisher date: Sat, 18 Jul 2026 20:17:30 GMT

Read the original announcement

Revision history

25 Oct 2026DEBIAN-CVE-2026-53994 · Revision 1Source updated