CVE-2026-48769: Incus has an arbitrary file write on its client due to trusted image hash

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) < 7.2.0, fixed in 7.2.0. Check your lockfile, including transitive dependencies.

What it is

Incus is a system container and virtual machine manager. Prior to version 7.2.0, 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. Version 7.2.0 patches the issue.

From the GitHub advisory

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/daemonimages.go:91-92 defaults fp to the caller-controlled alias string. - cmd/incusd/daemonimages.go:333-335 builds destName := filepath.Join(destDir, fp). - cmd/incusd/daemonimages.go:469-523 enters the direct protocol branch, opens destName with os.Create(), and copies the HTTP response into that file. - cmd/incusd/daemonimages.go:528-532 validates the SHA-256 only after the file has already been created and populated. - cmd/incusd/daemonimages.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.

Weakness type: CWE-20.

Product: github.com/lxc/incus/v7/cmd/incusd (Go) · Assigned by: GitHub_M · Published: 2026-08-21

Affected and fixed versions

Severity scores

• 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

• 2026-06-26 — GitHub-reviewed advisory GHSA-f6m5-xw2g-xc4x published (critical)
• 2026-08-21 — CVE record last updated
• 2026-08-21 — 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

1. GitHub Advisory GHSA-f6m5-xw2g-xc4x github.com
2. CVE.org record CVE-2026-48769 cve.org
3. NVD entry CVE-2026-48769 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com

Critical Go advisories · Today’s Security Digest