A high‑risk elevation‑of‑privilege vulnerability affecting Microsoft Azure Arc has been disclosed and patched — but the public tracking and identifier details are messy, and administrators must act now to confirm which of their Arc installations are affected, apply vendor fixes, and harden local access to prevent post‑compromise escalation. The flaw is described as a command‑injection style weakness that lets an authorized local user inject special command elements during Azure Arc installation/configuration and thereby elevate privileges on the host; multiple vulnerability trackers and vendor advisories list the Azure Arc item under a CVE that differs from the identifier supplied in the original report, so operators must verify the MSRC advisory and their inventory carefully.
Azure Arc is Microsoft’s hybrid management platform that extends Azure management, policy, and governance to on‑premises servers, Kubernetes clusters, and other resources. Because Arc is used to administer and automate management tasks across many systems, a flaw in Arc’s installer or agent that allows local privilege escalation is particularly dangerous: a local foothold can turn into administrative control of management tooling, which in turn can damage a broad estate.
Public advisories describe the technical class of the problem as improper neutralization of special elements used in a command (CWE‑77 / command injection), which effectively means user‑controllable input is incorporated into commands or scripts without adequate sanitization. Multiple vulnerability trackers and incident summaries report a high severity rating for the Azure Arc item and list the practical exploitability as requiring local access but only low privileges to start — conditions that make Azure Arc a high‑value target inside compromised or multi‑tenant environments. Important verification note up front: the CVE identifier you provided (CVE‑2025‑55316) points to an MSRC advisory URL, but public vulnerability feeds and coverage of the Azure Arc installer issue predominantly index the problem under CVE‑2025‑26627. The MSRC site uses a JavaScript application to render advisories and may present pages under multiple internal identifiers; however, administrators should not rely on a single numeric label — instead, confirm the advisory details on the MSRC page and cross‑check product/version data against vendor and industry trackers.
Background / Overview
Azure Arc is Microsoft’s hybrid management platform that extends Azure management, policy, and governance to on‑premises servers, Kubernetes clusters, and other resources. Because Arc is used to administer and automate management tasks across many systems, a flaw in Arc’s installer or agent that allows local privilege escalation is particularly dangerous: a local foothold can turn into administrative control of management tooling, which in turn can damage a broad estate.Public advisories describe the technical class of the problem as improper neutralization of special elements used in a command (CWE‑77 / command injection), which effectively means user‑controllable input is incorporated into commands or scripts without adequate sanitization. Multiple vulnerability trackers and incident summaries report a high severity rating for the Azure Arc item and list the practical exploitability as requiring local access but only low privileges to start — conditions that make Azure Arc a high‑value target inside compromised or multi‑tenant environments. Important verification note up front: the CVE identifier you provided (CVE‑2025‑55316) points to an MSRC advisory URL, but public vulnerability feeds and coverage of the Azure Arc installer issue predominantly index the problem under CVE‑2025‑26627. The MSRC site uses a JavaScript application to render advisories and may present pages under multiple internal identifiers; however, administrators should not rely on a single numeric label — instead, confirm the advisory details on the MSRC page and cross‑check product/version data against vendor and industry trackers.
What the advisory says (technical summary)
The flaw in plain English
- The vulnerability is a command injection / improper neutralization of special elements issue in the Azure Arc installer/agent.
- An authorized local user — e.g., a low‑privileged account that can run the installer or interact with install/configuration scripts — can provide crafted inputs that are interpreted as part of a command line.
- Because those inputs are not correctly neutralized or parameterized, the attacker can cause additional commands or arguments to be executed at higher privilege levels, achieving local elevation of privilege.
Core metadata that matters to defenders
- Typical CVSS v3.1 vector published: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H, base score 7.0 (High) in multiple trackers. This reflects a local attack vector, non‑interactive exploitability once the conditions are met, and high impact on confidentiality, integrity and availability if successfully executed.
- Publicly reported affected product strings: Azure Arc (installer/agent), with version ranges often listed as prior to a specific patched release (trackers show examples like version < 1.0.10). Operators must match their installed Arc/agent versions against vendor advisory data.
- Exploitation prerequisites: local access and the ability to run or influence installer/configuration inputs; exploitation does not appear to be remotely unauthenticated or wormable. That said, a remote compromise that grants local code execution (e.g., a vulnerable container, compromised CI runner, or stolen credentials) could be chained to this flaw.
Why this matters: real‑world risk scenarios
Even though the attack vector is local, there are several high‑risk deployment patterns that make this vulnerability urgent:- Compromised low‑privilege accounts or service accounts: Attackers who already have a user account (phished credentials, stolen keys, or compromised CI/automation jobs) can use the Arc installer weakness to escalate to local administrative privileges. That can lead to lateral movement and persistence.
- CI/CD runners and build farms: Shared or multi‑tenant automation systems often run as limited users but may invoke installers or management agents. A single malicious job or container escape could exploit the Arc installation process.
- Management plane amplification: If a compromised host runs Arc and Arc is trusted by identity and management processes, an attacker who escalates privileges locally may be able to modify management‑plane configuration, deploy malicious extensions, or exfiltrate credentials used to access other resources. This amplifies the blast radius.
Verified technical specifics and cross‑checks
To avoid dependency on a single tracker or a potentially mistyped CVE:- Microsoft’s Security Update Guide is the canonical advisory source for vendor‑authored remediation information; the MSRC entry for the identifier you provided renders via JavaScript and should be consulted directly to confirm the exact text and fix guidance.
- Independent CVE aggregators and vulnerability databases list the Azure Arc installer/agent command injection issue under CVE‑2025‑26627 with CWE‑77 and the CVSS details summarized above. Sources confirming this include cve.circl (aggregator), Tenable, and Recorded Future. (tenable.com, bleepingcomputer.com, msrc.microsoft.com, msrc.microsoft.com, cve.circl.lu, msrc.microsoft.com, cve.circl.lu, msrc.microsoft.com, cve.circl.lu, msrc.microsoft.com, recordedfuture.com)
Source: MSRC Security Update Guide - Microsoft Security Response Center
