# What is CVE-2023-3138?

> CVE-2023-3138 is a high-severity flaw (CVSS 7.5) in Libx11 from X.org, published on 28 June 2023. 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 1.7%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2023-3138

## At a glance

- **Verdict:** Plan it in. No sign of exploitation and a low forecast. Patch it in your normal update cycle.
- **Precursor Intelligence risk score:** 48 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:** 1.7% (latest exploit-likelihood forecast)
- **Published:** 28 June 2023
- **Record last updated:** 8 December 2023
- **Main product:** Libx11 from X.org
- **Affected products:** 2

## What is CVE-2023-3138? In plain terms

It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can take it offline.

### The official description

A vulnerability was found in libX11. The security flaw occurs because the functions in src/InitExt.c in libX11 do not check that the values provided for the Request, Event, or Error IDs are within the bounds of the arrays that those functions write to, using those IDs as array indexes. They trust that they were called with values provided by an Xserver adhering to the bounds specified in the X11 protocol, as all X servers provided by X.Org do. As the protocol only specifies a single byte for these values, an out-of-bounds value provided by a malicious server (or a malicious proxy-in-the-middle) can only overwrite other portions of the Display structure and not write outside the bounds of the Display structure itself, possibly causing the client to crash with this memory corruption.

### What kind of flaw is it?

- CWE-787: Out-of-bounds Write
- CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer

### 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
- Does someone have to click: No, nobody has to do anything
- What an attacker gets: Can take it offline

Severity vector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`

## Is CVE-2023-3138 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 1.7%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 1.7%, 1.7%, 1.7%, 1.7%, 1.7%, 1.7%, 1.7%.

### Timeline

- 28 June 2023: Published
- 8 December 2023: Record last updated

### How Precursor Intelligence ranks it

CVE-2023-3138 scores **48 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-2023-3138?

The published record lists 2 products. Versions are as published: "before 1.8.6" means every version up to, but not including, 1.8.6.

- [Libx11](https://www.precursorintelligence.com/product/x.org/libx11) by [X.org](https://www.precursorintelligence.com/vendors/x.org) (Application): before 1.8.6
- [Enterprise Linux](https://www.precursorintelligence.com/product/redhat/enterprise_linux) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 8.0, 9.0

## How do I fix CVE-2023-3138?

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

- [gitlab.freedesktop.org](https://gitlab.freedesktop.org/xorg/lib/libx11/-/commit/304a654a0d57bf0f00d8998185f0360332cfa36c) (Patch)
- [lists.x.org](https://lists.x.org/archives/xorg-announce/2023-June/003406.html) (Mailing list, Patch)
- [lists.x.org](https://lists.x.org/archives/xorg-announce/2023-June/003407.html) (Mailing list, Patch)
- [access.redhat.com](https://access.redhat.com/security/cve/CVE-2023-3138) (Third-party advisory)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20231208-0008/)

## Questions

### What is CVE-2023-3138?

CVE-2023-3138 is a high-severity flaw in Libx11 from X.org, published on 28 June 2023. It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can take it offline.

### How serious is CVE-2023-3138?

It scores 7.5 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2023-3138 is 48 out of 100, which is Medium. Its action is "Plan remediation". No sign of exploitation and a low forecast. Patch it in your normal update cycle.

### Is CVE-2023-3138 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 1.7%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2023-3138 affect?

For Libx11 from X.org: before 1.8.6. The record lists 2 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2023-3138?

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-2023-3138 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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