CVE-1999-0910: Microsoft Site Server and Commercial Internet System (MCIS) do not set an expiration for a cookie, which could

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MEDIUM 5.0WATCHLISTDOWNGRADEDOWNGRADEDOWNGRADE

CVE-1999-0910 is a medium-severity flaw (CVSS 5.0) affecting commercial internet system, site server, site server commerce. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Microsoft Site Server and Commercial Internet System (MCIS) do not set an expiration for a cookie, which could then be cached by a proxy and inadvertently used by a different user.

Why this priority

EPSS top 7%: very likely to be exploited
On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.0 (Medium)
EPSS exploit chance	5.8% (top 7%)
CISA exploited list	No
Published	1999-09-10
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: microsoft

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

1999-09-10 04:00 UTCPublished CVE record published
2026-06-16 21:49 UTCUpdated Record last modified

microsoft commercial internet system DOWNGRADE

Affected: 2.0 · 2.5

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.0

1. Check installed version

apt-cache policy commercial-internet-system || rpm -q commercial-internet-system || commercial-internet-system --version

2. No fixed release: DOWNGRADE to a release before 2.0 (Debian / Ubuntu)

apt-cache madison commercial-internet-system sudo apt install commercial-internet-system=<VERSION_BEFORE_2.0> sudo apt-mark hold commercial-internet-system

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

dnf --showduplicates list commercial-internet-system sudo dnf downgrade commercial-internet-system-<VERSION_BEFORE_2.0> sudo dnf versionlock add commercial-internet-system

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 site server DOWNGRADE

Affected: 3.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.0 (Debian / Ubuntu)

apt-cache madison site-server sudo apt install site-server=<VERSION_BEFORE_3.0> sudo apt-mark hold site-server

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

dnf --showduplicates list site-server sudo dnf downgrade site-server-<VERSION_BEFORE_3.0> sudo dnf versionlock add site-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 site server commerce DOWNGRADE

Affected: 3.0 alpha

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.0

1. Check installed version

apt-cache policy site-server-commerce || rpm -q site-server-commerce || site-server-commerce --version

2. No fixed release: DOWNGRADE to a release before 3.0 (Debian / Ubuntu)

apt-cache madison site-server-commerce sudo apt install site-server-commerce=<VERSION_BEFORE_3.0> sudo apt-mark hold site-server-commerce

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

dnf --showduplicates list site-server-commerce sudo dnf downgrade site-server-commerce-<VERSION_BEFORE_3.0> sudo dnf versionlock add site-server-commerce

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.

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-1999-0910?

commercial internet system: downgrade or apply the listed mitigation; site server: downgrade or apply the listed mitigation; site server commerce: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-1999-0910 being exploited?

CVE-1999-0910 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-1999-0910 affect?

CVE-1999-0910 affects commercial internet system, site server, site server commerce. Severity is medium (CVSS 5.0). Microsoft Site Server and Commercial Internet System (MCIS) do not set an expiration for a cookie, which could then be cached by a proxy and inadvertently used by a different user.

How urgent is CVE-1999-0910?

Priority 46/100. EPSS top 7%: very likely to be exploited; On your watchlist

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References

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