CVE-2026-96940: Weak authentication in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a ne

Q: How do I fix CVE-2026-96940?

exchange server: downgrade or apply the listed mitigation; exchange server subscription edition: upgrade to 15.02.2562.053. Exact commands for each OS are on this page.

Q: Is CVE-2026-96940 being exploited?

CVE-2026-96940 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-96940 affect?

CVE-2026-96940 affects exchange server, exchange server subscription edition. Severity is high (CVSS 8.8). Weak authentication in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.

Q: How urgent is CVE-2026-96940?

Priority 57/100. High severity; On your watchlist

This month

HIGH 8.8WATCHLISTDOWNGRADEUPGRADE

CVE-2026-96940 is a high-severity flaw (CVSS 8.8) affecting exchange server, exchange server subscription edition. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Weak authentication in Microsoft Exchange Server 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	2.7% (top 14%)
CISA exploited list	No
Weakness	CWE-1390
Published	2026-10-02
Last modified	2026-10-15

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-10-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-10-02 19:16 UTCPublished CVE record published
2026-10-15 02:35 UTCUpdated Record last modified

microsoft exchange server DOWNGRADE

Affected: 2016 cumulative_update_23 · 2019 cumulative_update_14 · 2019 cumulative_update_15

Fixed in: no fixed release known

Safe to downgrade to: a release before 2016

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2016 (Debian / Ubuntu)

apt-cache madison exchange-server sudo apt install exchange-server=<VERSION_BEFORE_2016> sudo apt-mark hold exchange-server

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list exchange-server sudo dnf downgrade exchange-server-<VERSION_BEFORE_2016> sudo dnf versionlock add exchange-server

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

microsoft exchange server subscription edition UPGRADE

Affected: < 15.02.2562.053

Fixed in: 15.02.2562.053

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy exchange-server-subscription-edition || rpm -q exchange-server-subscription-edition || exchange-server-subscription-edition --version

2. UPGRADE to 15.02.2562.053 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade exchange-server-subscription-edition

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade exchange-server-subscription-edition

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora ELN · edk2 · FIXED · 20260812-12.eln159 · FEDORA-2026-e316b6370a · source

sudo dnf upgrade --advisory=FEDORA-2026-e316b6370a

Fedora 46 · perl-Mojo-DOM58 · FIXED · 3.003-1.fc46 · FEDORA-2026-d5412af3de · source

sudo dnf upgrade --advisory=FEDORA-2026-d5412af3de

Microsoft Exchange Server 2019 Cumulative Update 14 · KB5129957 · FIXED · 15.02.1544.048 · KB5129957

Install KB5129957 via Windows Update, then verify: Get-HotFix -Id KB5129957

Microsoft Exchange Server 2016 Cumulative Update 23 · KB5129958 · FIXED · 15.01.2507.075 · KB5129958

Install KB5129958 via Windows Update, then verify: Get-HotFix -Id KB5129958

Microsoft Exchange Server Subscription Edition RTM · KB5129955 · FIXED · 15.02.2562.053 · KB5129955 · source

Install KB5129955 via Windows Update, then verify: Get-HotFix -Id KB5129955

Microsoft Exchange Server 2019 Cumulative Update 15 · KB5129956 · FIXED · 15.02.1748.053 · KB5129956

Install KB5129956 via Windows Update, then verify: Get-HotFix -Id KB5129956

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: HORKimhab/CVE-2026-96940 (1 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-2026-96940?

exchange server: downgrade or apply the listed mitigation; exchange server subscription edition: upgrade to 15.02.2562.053. Exact commands for each OS are on this page.

Is CVE-2026-96940 being exploited?

CVE-2026-96940 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-2026-96940 affect?

CVE-2026-96940 affects exchange server, exchange server subscription edition. Severity is high (CVSS 8.8). Weak authentication in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.

How urgent is CVE-2026-96940?

Priority 57/100. High severity; On your watchlist

Software pages

Microsoft Exchange vulnerabilities

Related CVEs

CVE-2026-42897 HIGH 8.1 EXPLOITED DOWNGRADE UPGRADE Microsoft Exchange Server Cross-Site Scripting Vulnerability

References

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