Security Digest · Vulnerability record
CVE-2026-48753: Incus has an arbitrary file write via path traversal in S3 multipart upload
Incus is a system container and virtual machine manager.
CVSS 9.9 Critical EPSS 0.7% · p54
Should you act?
Critical, preconditions apply
Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.7%, percentile 54: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 54% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Needs an account (low (any account)). Exposure depends on who can log in.
- Only applies if your dependency tree includes
github.com/lxc/incus/v7/cmd/incusd(Go) < 7.1.0, fixed in 7.1.0. Check your lockfile, including transitive dependencies.
What it is
Incus is a system container and virtual machine manager. Prior to version 7.1.0, the S3 protocol upload endpoint is vulnerable to path traversal and allows creation of arbitrary files on the host. This behavior could lead to arbitrary command execution. Version 7.1.0 fixes the issue.
From the GitHub advisory
Summary
The S3 protocol upload endpoint is vulnerable to path traversal and allows creation of arbitrary files on the host. This behavior could lead to arbitrary command execution.
In internal/server/storage/s3/local/multipart.go, user-controlled upload ID is appended to the uploads directory unsanitized; https://github.com/lxc/incus/blob/40dd4f151d52c06b178482aa2518abfb9df3e6fb/internal/server/storage/s3/local/multipart.go#L33
PoC
Setup
Weakness type: CWE-73.
Product: github.com/lxc/incus/v7/cmd/incusd (Go) · Assigned by: GitHub_M · Published: 2026-08-21
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| Go | github.com/lxc/incus/v7/cmd/incusd | < 7.1.0 | 7.1.0 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| lxc | incus | < 7.1.0 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 9.9 Critical | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H |
| GitHub | 3.1 | 9.9 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: low (any account)
- User interaction: none
- Scope: changed (can affect other components)
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc, automatable no, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.73% probability of exploitation activity in the next 30 days; percentile 54.
Timeline
- — GitHub-reviewed advisory GHSA-ccjc-4qc3-jxqc published (critical)
- — CVE record last updated
- — CVE record published by GitHub_M
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-ccjc-4qc3-jxqc github.com
- CVE.org record CVE-2026-48753 cve.org
- NVD entry CVE-2026-48753 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com