How severe is CVE-2023-6209?

CVE-2023-6209 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2023-6209 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-6209?

CVE-2023-6209 primarily affects Mozilla Firefox. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2023-6209?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2023-6209 published?

CVE-2023-6209 was published on 2023-11-21 and last updated on 2026-06-17.

CVE-2023-6209

CVE-2023-6209 is a medium-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-22.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 1% (69th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-22
Affected product: Mozilla Firefox
Published: 2023-11-21
Last modified: 2026-06-17

Description

Relative URLs starting with three slashes were incorrectly parsed, and a path-traversal "/../" part in the path could be used to override the specified host. This could contribute to security problems in web sites. This vulnerability affects Firefox < 120, Firefox ESR < 115.5.0, and Thunderbird < 115.5.

Frequently asked questions

What is CVE-2023-6209?: Relative URLs starting with three slashes were incorrectly parsed, and a path-traversal "/../" part in the path could be used to override the specified host. This could contribute to security problems in web sites. This vulnerability affects Firefox < 120, Firefox ESR < 115.5.0, and Thunderbird < 115.5.
How severe is CVE-2023-6209?: CVE-2023-6209 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2023-6209 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-6209?: CVE-2023-6209 primarily affects Mozilla Firefox. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2023-6209?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2023-6209 published?: CVE-2023-6209 was published on 2023-11-21 and last updated on 2026-06-17.

References

Affected products (6)

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:12.0:*:*:*:*:*:*:*

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