CVE-2026-54998: Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over

This month

HIGH 8.8WATCHLISTMITIGATE

CVE-2026-54998 is a high-severity flaw (CVSS 8.8) affecting exchange online. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.8% (top 44%)
CISA exploited list	No
Weakness	CWE-863
Published	2026-07-02
Last modified	2026-10-25

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-02 23:16 UTCPublished CVE record published
2026-10-25 21:10 UTCUpdated Record last modified

microsoft exchange online MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy exchange-online || rpm -q exchange-online || exchange-online --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · rust-opendal-core · FIXED · 0.59.1-2.fc46 · FEDORA-2026-4607543819 · source

sudo dnf upgrade --advisory=FEDORA-2026-4607543819

Fedora ELN · velocitty · FIXED · 1.0.3-2.eln159 · FEDORA-2026-edae8cd295 · source

sudo dnf upgrade --advisory=FEDORA-2026-edae8cd295

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: sentinel-aidefense/CVE-2026-54998-exp (3 stars)

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-54998?

exchange online: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-54998 being exploited?

CVE-2026-54998 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-54998 affect?

CVE-2026-54998 affects exchange online. Severity is high (CVSS 8.8). Incorrect authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a network.

How urgent is CVE-2026-54998?

Priority 50/100. High severity; On your watchlist

Software pages

Microsoft Exchange vulnerabilities

Related CVEs

CVE-2026-48582 CRITICAL 9.6 MITIGATE Missing authorization in Microsoft Exchange Online allows an authorized attacker to elevate privileges over a
CVE-2026-56191 CRITICAL 10.0 MITIGATE Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over

References

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