# CVE-2026-54998: Microsoft Exchange Online Elevation of Privilege Vulnerability

> An authorized attacker can elevate privileges in Microsoft Exchange Online due to incorrect authorization checks.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 Jul 2026
- **Updated:** 8 Oct 2026
- **Also known as:** GHSA-phr2-vr74-whpx

## What is CVE-2026-54998?

CVE-2026-54998 is a high-severity vulnerability in Microsoft Exchange Online, published on 2 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-54998?

It affects 1 product.


Products: Microsoft Exchange Online.

## How do I fix CVE-2026-54998?

No fix has been published for CVE-2026-54998 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-54998 being exploited?

There is no known exploitation of CVE-2026-54998 in the wild and no public exploit code.

Public exploit code:

- CVE-2026-54998 RCE Exploit (github_poc): https://github.com/sentinel-aidefense/CVE-2026-54998-exp

## Other vulnerabilities in Microsoft Exchange Online

- [CVE-2026-65801](https://insights.sbomify.com/CVE-2026-65801/): Microsoft Exchange Online Elevation of Privilege Vulnerability (critical 10.0)
- [CVE-2026-56191](https://insights.sbomify.com/CVE-2026-56191/): Microsoft Exchange Online Tampering Vulnerability (critical 10.0)
- [CVE-2026-48582](https://insights.sbomify.com/CVE-2026-48582/): Microsoft Exchange Online Elevation of Privilege Vulnerability (critical 9.6)
- [CVE-2026-48579](https://insights.sbomify.com/CVE-2026-48579/): Microsoft Exchange Online Information Disclosure Vulnerability (critical 9.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54998 and fix it if it is affected.

What it is: CVE-2026-54998 is a high-severity vulnerability in Microsoft Exchange Online, published on 2 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-54998 in the wild and no public exploit code.

Affected product: Microsoft Exchange Online. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-54998/ (Markdown: https://insights.sbomify.com/CVE-2026-54998/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54998
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54998
- OSV: https://osv.dev/vulnerability/CVE-2026-54998

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54998/
Summaries are generated and may contain mistakes; the official description above is the record.