# What is CVE-2004-0121?

> CVE-2004-0121 is a high-severity flaw (CVSS 7.5) in Outlook from Microsoft, published on 15 April 2004. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 48%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2004-0121

## At a glance

- **Verdict:** Fix this soon. Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.
- **Precursor Intelligence risk score:** 43 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes.
- **Severity:** High (CVSS 7.5 out of 10)
- **Known to be exploited:** No, not on the list of flaws known to be exploited today
- **Chance of use in the next 30 days:** 48% (latest exploit-likelihood forecast)
- **Published:** 15 April 2004
- **Record last updated:** 16 June 2026
- **Main product:** Outlook from Microsoft
- **Affected products:** 2

## What is CVE-2004-0121? In plain terms

It can be attacked from anywhere on the internet without logging in. If it works, the attacker can read some data, change some data and slow it down.

### The official description

Argument injection vulnerability in Microsoft Outlook 2002 does not sufficiently filter parameters of mailto: URLs when using them as arguments when calling OUTLOOK.EXE, which allows remote attackers to use script code in the Local Machine zone and execute arbitrary programs.

### What kind of flaw is it?

- CWE-88: Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')

### How an attack on it works

- Where an attacker can be: Anywhere on the internet
- How hard it is to pull off: Easy: no special conditions
- Login needed first: No login needed
- What an attacker gets: Can read some data, change some data and slow it down

Severity vector: `AV:N/AC:L/Au:N/C:P/I:P/A:P`

## Is CVE-2004-0121 being exploited? Not that we know of

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 48%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 48%, 48%, 48%, 48%, 48%, 48%, 48%.

### Timeline

- 15 April 2004: Published
- 9 August 2023: Exploit likelihood fell
- 11 June 2025: Exploit likelihood jumped
- 16 June 2026: Record last updated

### How Precursor Intelligence ranks it

CVE-2004-0121 scores **43 out of 100 (Medium)**, with the action "Plan remediation".

Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less:

- Evidence it is being exploited: biggest factor
- How severe it is: strong factor
- How widely exposed it is: smaller factor
- Threat activity around it: smaller factor

85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it.

## Who is affected by CVE-2004-0121?

The published record lists 2 products.

- [Outlook](https://www.precursorintelligence.com/product/microsoft/outlook) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Application): 2002-sp2
- [Office](https://www.precursorintelligence.com/product/microsoft/office) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Application): xp-sp2

## How do I fix CVE-2004-0121?

1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list.
2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisories and patch notes first in the list.
3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in.
4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood.

### References

- [idefense.com](http://www.idefense.com/application/poi/display?id=79&type=vulnerabilities) (Broken link, Patch, Vendor advisory)
- [securityfocus.com](http://www.securityfocus.com/bid/9827) (Broken link, Exploit, Patch, Third-party advisory, Vulnerability database, Vendor advisory)
- [docs.microsoft.com](https://docs.microsoft.com/en-us/security-updates/securitybulletins/2004/ms04-009) (Patch, Vendor advisory)
- [kb.cert.org](http://www.kb.cert.org/vuls/id/305206) (Mitigation, Third-party advisory, Government resource)
- [marc.info](http://marc.info/?l=bugtraq&m=107893704602842&w=2) (Third-party advisory)
- [ciac.org](http://www.ciac.org/ciac/bulletins/o-096.shtml) (Broken link)
- [us-cert.gov](http://www.us-cert.gov/cas/techalerts/TA04-070A.html) (Broken link, Third-party advisory, Government resource)
- [exchange.xforce.ibmcloud.com](https://exchange.xforce.ibmcloud.com/vulnerabilities/15414) (Third-party advisory, Vulnerability database)
- [exchange.xforce.ibmcloud.com](https://exchange.xforce.ibmcloud.com/vulnerabilities/15429) (Third-party advisory, Vulnerability database)
- [oval.cisecurity.org](https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A843) (Broken link)

## Questions

### What is CVE-2004-0121?

CVE-2004-0121 is a high-severity flaw in Outlook from Microsoft, published on 15 April 2004. It can be attacked from anywhere on the internet without logging in. If it works, the attacker can read some data, change some data and slow it down.

### How serious is CVE-2004-0121?

It scores 7.5 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2004-0121 is 43 out of 100, which is Medium. Its action is "Plan remediation". Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.

### Is CVE-2004-0121 being exploited?

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 48%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2004-0121 affect?

For Outlook from Microsoft: 2002-sp2. The record lists 2 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2004-0121?

Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet.

## Does CVE-2004-0121 affect you?

Precursor Intelligence keeps checking for you:

- **Tell us what you run.** Pick your software from a list, or let us work it out from your website.
- **We match it to every flaw.** Over 400,000 published flaws, checked against your list.
- **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it.
- **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools.

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