How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

374,644

Total vulnerabilities in the database

rclone local `--metadata` applies attacker-controlled mode/uid - setuid binary planted from an untrusted remote — github.com/rclone/rclone

Incorrect Permission Assignment for Critical Resource

Summary

When writing an object with metadata, the local backend applies the source-supplied mode, uid, and gid verbatim: it parses mode as an octal integer and passes it straight into os.Chmod(o.path, os.FileMode(umode)), and passes uid/gid straight into os.Chown. The value is never masked to permission bits, so any value with Go's ModeSetuid (1<<23) or ModeSetgid (1<<22) bit set causes the setuid/setgid bit to be applied. Because both the file content and its metadata come from the (attacker-controlled) source remote, an attacker stores a binary of their choosing with mode = 40000755 (and uid = 0); when the victim runs rclone copy -M <remote>: /dest, rclone writes the attacker's binary and makes it setuid. If the victim runs rclone as root (typical for system backup/restore), the uid=0 chown plus setuid produces a root-owned setuid binary with attacker content — any local user then escalates to root. When rclone runs as a non-root service user, the planted setuid binary is owned by that user, giving any local user that user's privileges (lateral escalation / persistent backdoor).

Details

backend/local/metadata.go, writeMetadataToFile():

uid, hasUID := o.parseMetadataInt(m, &quot;uid&quot;, 10)
gid, hasGID := o.parseMetadataInt(m, &quot;gid&quot;, 10)
if hasUID {
    ...
    err = os.Chown(o.path, uid, gid)        // source-controlled owner, no same-uid guard
}
mode, hasMode := o.parseMetadataInt(m, &quot;mode&quot;, 8)
if hasMode &amp;&amp; mode &gt;= 0 {
    umode := uint(mode)
    if umode &lt;= math.MaxUint32 {
        err = os.Chmod(o.path, os.FileMode(umode))   // &lt;-- raw value; ModeSetuid/ModeSetgid NOT masked off
    }
}

os.Chmod/os.FileMode honor ModeSetuid/ModeSetgid/ModeSticky. There is no &^ (os.ModeSetuid|os.ModeSetgid) mask and no check that the source is trusted, so an attacker-chosen mode string sets those bits on the freshly written, attacker-controlled file. (Note: a legitimate local source reports mode in unix st_mode layout e.g. 0106755, whose bit 1<<23 is unset, so honest copies happen to drop setuid — but the attacker supplies the Go-FileMode layout 40000755 directly, which sets it.)

PoC

Get the official stable binary:

curl -fsSLO https://downloads.rclone.org/v1.74.3/rclone-v1.74.3-linux-amd64.zip
unzip -j rclone-v1.74.3-linux-amd64.zip &#039;*/rclone&#039; -d .      # ./rclone -&gt; v1.74.3

Create a payload (the attacker-controlled binary content) and copy it with the malicious mode metadata:

mkdir -p msrc mdst &amp;&amp; cp /bin/true msrc/payload
./rclone copy -M --metadata-set mode=40000755 msrc mdst       # 40000755 = Go FileMode setuid|0755

Observe — the destination file is now setuid:

stat -c &#039;%A %a&#039; mdst/payload
-rwsr-xr-x 4755                                               # &#039;s&#039; = setuid bit SET on attacker binary

Variants: mode=20000755 → setgid (-rwxr-sr-x); mode=60000755 → both (-rwsr-sr-x). With rclone run as root and the source object also carrying uid=0/gid=0, the file is chown'd root:root, yielding a root-owned setuid binary executable by any local user.

Impact

A victim performing a metadata-preserving copy/restore (-M) from an untrusted or compromised remote installs an attacker-chosen executable with the setuid/setgid bit set. Run as root (system backup/restore, the common case for --metadata), this is a root-owned setuid root backdoor executable by any local user → local privilege escalation to root. Run as a non-root user, it is a setuid backdoor for that service account. The companion uid/gid application lets a root-run transfer also reassign ownership of written files arbitrarily.

Remediation

Mask special bits before applying mode from metadata — os.Chmod(o.path, os.FileMode(umode).Perm()) (or umode & 0o777) — and do not honor setuid/setgid/sticky from source metadata; gate uid/gid/setuid application behind an explicit opt-in (e.g. --local-metadata-set-ownership) that is off by default, and document that -M from untrusted remotes must not restore privileged bits. Regression test: copying an object with mode=40000755/uid=0 must produce a non-setuid, caller-owned file unless the opt-in is set.

Published: Aug 5, 2026
Updated: Aug 6, 2026
GHSA: GHSA-945v-v9p3-v5xw
Severity: Low
Exploit:
CISA KEV:

CVSS v3:

Severity: Low
Score: 3.6
AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

CWEs:

CWE-732

Affected Software
References

Software	From	Fixed in
github.com/rclone/rclone	-	1.74.4

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.