# What is CVE-2023-38545?

> CVE-2023-38545 is a critical-severity flaw (CVSS 9.8) in Libcurl from Haxx, published on 18 October 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 79%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2023-38545

## 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:** 69 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes.
- **Severity:** Critical (CVSS 9.8 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:** 79% (latest exploit-likelihood forecast)
- **Published:** 18 October 2023
- **Record last updated:** 13 February 2025
- **Main product:** Libcurl from Haxx
- **Affected products:** 13

## What is CVE-2023-38545? 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 read data, change data and take it offline.

### The official description

This flaw makes curl overflow a heap based buffer in the SOCKS5 proxy
handshake.

When curl is asked to pass along the host name to the SOCKS5 proxy to allow
that to resolve the address instead of it getting done by curl itself, the
maximum length that host name can be is 255 bytes.

If the host name is detected to be longer, curl switches to local name
resolving and instead passes on the resolved address only. Due to this bug,
the local variable that means "let the host resolve the name" could get the
wrong value during a slow SOCKS5 handshake, and contrary to the intention,
copy the too long host name to the target buffer instead of copying just the
resolved address there.

The target buffer being a heap based buffer, and the host name coming from the
URL that curl has been told to operate with.

### What kind of flaw is it?

- CWE-787: Out-of-bounds Write

### 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 read data, change data and take it offline

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

## Is CVE-2023-38545 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 79%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 78%, 79%, 79%, 79%, 79%, 79%, 79%.

### Timeline

- 18 October 2023: Published
- 13 February 2025: Record last updated
- 11 June 2025: Exploit likelihood fell
- 19 November 2025: Exploit likelihood jumped

### How Precursor Intelligence ranks it

CVE-2023-38545 scores **69 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-2023-38545?

The published record lists 13 products. Versions are as published: "7.69.0 to before 8.4.0" means from 7.69.0 up to, but not including, 8.4.0.

- [Libcurl](https://www.precursorintelligence.com/product/haxx/libcurl) by [Haxx](https://www.precursorintelligence.com/vendors/haxx) (Application): 7.69.0 to before 8.4.0
- [Active Iq Unified Manager](https://www.precursorintelligence.com/product/netapp/active_iq_unified_manager) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Fedora](https://www.precursorintelligence.com/product/fedoraproject/fedora) by [Fedoraproject](https://www.precursorintelligence.com/vendors/fedoraproject) (Operating system): 37
- [Oncommand Insight](https://www.precursorintelligence.com/product/netapp/oncommand_insight) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Oncommand Workflow Automation](https://www.precursorintelligence.com/product/netapp/oncommand_workflow_automation) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Windows 10 1809](https://www.precursorintelligence.com/product/microsoft/windows_10_1809) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): before 10.0.17763.5122
- [Windows 10 21H2](https://www.precursorintelligence.com/product/microsoft/windows_10_21h2) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): before 10.0.19044.3693
- [Windows 10 22H2](https://www.precursorintelligence.com/product/microsoft/windows_10_22h2) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): before 10.0.19045.3693
- [Windows 11 21H2](https://www.precursorintelligence.com/product/microsoft/windows_11_21h2) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): before 10.0.22000.2600
- [Windows 11 22H2](https://www.precursorintelligence.com/product/microsoft/windows_11_22h2) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): before 10.0.22621.2715
- [Windows 11 23H2](https://www.precursorintelligence.com/product/microsoft/windows_11_23h2) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): before 10.0.22631.2715
- [Windows Server 2019](https://www.precursorintelligence.com/product/microsoft/windows_server_2019) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): before 10.0.17763.5122
- [Windows Server 2022](https://www.precursorintelligence.com/product/microsoft/windows_server_2022) by [Microsoft](https://www.precursorintelligence.com/vendors/microsoft) (Operating system): before 10.0.20348.2113

## How do I fix CVE-2023-38545?

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

- [curl.se](https://curl.se/docs/CVE-2023-38545.html) (Patch, Third-party advisory)
- [secpod.com](https://www.secpod.com/blog/high-severity-heap-buffer-overflow-vulnerability/) (Patch, Third-party advisory)
- [seclists.org](http://seclists.org/fulldisclosure/2024/Jan/34) (Mailing list, Third-party advisory)
- [seclists.org](http://seclists.org/fulldisclosure/2024/Jan/37) (Mailing list, Third-party advisory)
- [seclists.org](http://seclists.org/fulldisclosure/2024/Jan/38) (Mailing list, Third-party advisory)
- [forum.vmssoftware.com](https://forum.vmssoftware.com/viewtopic.php?f=8&t=8868)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OGMXNRNSJ4ETDK6FRNU3J7SABXPWCHSQ/) (Mailing list, Third-party advisory)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20231027-0009/) (Third-party advisory)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20240201-0005/) (Third-party advisory)
- [support.apple.com](https://support.apple.com/kb/HT214036) (Third-party advisory)
- [support.apple.com](https://support.apple.com/kb/HT214057) (Third-party advisory)
- [support.apple.com](https://support.apple.com/kb/HT214058) (Third-party advisory)
- [support.apple.com](https://support.apple.com/kb/HT214063) (Third-party advisory)
- [github.com](https://github.com/UTsweetyfish/CVE-2023-38545)
- [github.com](https://github.com/bcdannyboy/CVE-2023-38545)
- [github.com](https://github.com/dbrugman/CVE-2023-38545-POC)

## Questions

### What is CVE-2023-38545?

CVE-2023-38545 is a critical-severity flaw in Libcurl from Haxx, published on 18 October 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 read data, change data and take it offline.

### How serious is CVE-2023-38545?

It scores 9.8 out of 10 on the CVSS severity scale, which is critical. Our risk score for CVE-2023-38545 is 69 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-2023-38545 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 79%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2023-38545 affect?

For Libcurl from Haxx: 7.69.0 to before 8.4.0. The record lists 13 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2023-38545?

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-2023-38545 affect you?

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- **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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