CVE-2023-6205: It was possible to cause the use of a MessagePort after it had already been freed, which could potentially have led to an exploitable crash. This vulnerability affects Firefox < 120, Firefox ESR < 115.5.0, and Thunderbird < 115.5.
CVE-2023-6205 is a vulnerability in It was possible to cause the use of a MessagePort after it had already been freed, which could potentially have led to an exploitable crash. This vulnerability affects Firefox < 120, Firefox ESR < 115.5.0, and Thunderbird < 115.5., rated Moderate by Microsoft, with a CVSS 3.1 base score of 6.5 (Medium). An attacker can exploit it remotely over the network, without any privileges and only if a user takes an action. Microsoft has not reported exploitation in the wild. The EPSS model estimates a 0.87% probability of exploitation activity in the next 30 days, higher than 59% of all scored vulnerabilities. Microsoft published it on 3 September 2025 in the November 2023 Patch Tuesday. It affects 1 product in 1 product family (Other).
Key facts
- CVE ID
- CVE-2023-6205
- Severity
- Medium CVSS 6.5
- Microsoft severity
- Moderate
- Exploited in the wild
- No
- Publicly disclosed
- No
- Weakness
- CWE-416
- EPSS
- 0.87% (percentile 59%)
- CISA KEV
- Not listed
- Released
- Last updated
- Patch Tuesday
- November 2023 Patch Tuesday
- Product families
- Other
CVSS score and vector
Microsoft scores CVE-2023-6205 at 6.5 (temporal 6.5) using CVSS 3.1. Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
| Metric | Value |
|---|---|
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | Required |
| Scope | Unchanged |
| Confidentiality impact | None |
| Integrity impact | None |
| Availability impact | High |
Frequently asked questions (Microsoft)
Is Azure Linux the only Microsoft product that includes this open-source library and is therefore potentially affected by this vulnerability?
One of the main benefits to our customers who choose to use the Azure Linux distro is the commitment to keep it up to date with the most recent and most secure versions of the open source libraries with which the distro is composed. Microsoft is committed to transparency in this work which is why we began publishing CSAF/VEX in October 2025. See this blog post for more information. If impact to additional products is identified, we will update the CVE to reflect this.
Affected products (1)
Other
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| 18469-17084 |
NIST NVD data
- NVD status
- Modified
- NVD CVSS
- 6.5 (MEDIUM)
- NVD weakness
- CWE-416
- Published to NVD
- NVD last modified
Affected configurations (CPE)
| Product | Vulnerable versions |
|---|---|
| firefox | before 120.0 |
| firefox esr | before 115.5.0 |
| thunderbird | before 115.5 |
| debian linux 10.0 | all listed versions |
| debian linux 11.0 | all listed versions |
| debian linux 12.0 | all listed versions |
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1854076 (Issue Tracking, Permissions Required)
- https://lists.debian.org/debian-lts-announce/2023/11/msg00017.html (Mailing List)
- https://lists.debian.org/debian-lts-announce/2023/11/msg00030.html
- https://www.debian.org/security/2023/dsa-5561 (Third Party Advisory)
- https://www.mozilla.org/security/advisories/mfsa2023-49/ (Release Notes, Vendor Advisory)
- https://www.mozilla.org/security/advisories/mfsa2023-50/ (Release Notes, Vendor Advisory)
- https://www.mozilla.org/security/advisories/mfsa2023-52/ (Release Notes, Vendor Advisory)
- https://bugzilla.mozilla.org/show_bug.cgi?id=1854076 (Issue Tracking, Permissions Required)
- https://lists.debian.org/debian-lts-announce/2023/11/msg00017.html (Mailing List)
- https://lists.debian.org/debian-lts-announce/2023/11/msg00030.html
- https://www.debian.org/security/2023/dsa-5561 (Third Party Advisory)
- https://www.mozilla.org/security/advisories/mfsa2023-49/ (Release Notes, Vendor Advisory)
- https://www.mozilla.org/security/advisories/mfsa2023-50/ (Release Notes, Vendor Advisory)
- https://www.mozilla.org/security/advisories/mfsa2023-52/ (Release Notes, Vendor Advisory)
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. | |
| 1.1 | Information published. |