Is CVE-2017-7823 in the CISA KEV catalog?

No. CVE-2017-7823 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2017-7823?

CVE-2017-7823 has a CVSS v3 base score of 5.4 (MEDIUM).

What is the EPSS score for CVE-2017-7823?

CVE-2017-7823 has an EPSS score of 1.47% (71th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2017-7823?

Upgrade firefox on debian unstable to 56.0-1 or later. Fixes are available for 6 affected products.

CVE & CISA-KEV Catalog

CVE-2017-7823

MEDIUMEPSS 71th pctl

5.4

CVSS v3

NVD

Description

The content security policy (CSP) "sandbox" directive did not create a unique origin for the document, causing it to behave as if the "allow-same-origin" keyword were always specified. This could allow a Cross-Site Scripting (XSS) attack to be launched from unsafe content. This vulnerability affects Firefox < 56, Firefox ESR < 52.4, and Thunderbird < 52.4.

CWE-79Cross-Site Scripting (XSS)

How to fix

Remediation Available

firefoxDebian

Fixed in:56.0-1CVE-2017-7823

firefoxUbuntu

Fixed in:56.0+build6-0ubuntu0.14.04.1USN-3435-1

Fixed in:56.0+build6-0ubuntu0.16.04.1USN-3435-1

thunderbirdUbuntu

Fixed in:1:52.4.0+build1-0ubuntu0.14.04.2USN-3436-1

Fixed in:1:52.4.0+build1-0ubuntu0.16.04.2USN-3436-1

DeveloperEditionWindows application

Affected:56.0Fixed in:56.0Mozilla

Affected:52.4.0Fixed in:52.4.0Mozilla

Mozilla Firefox (en-US)Windows application

Affected:56.0Fixed in:56.0Mozilla

Affected:52.4.0Fixed in:52.4.0Mozilla

Mozilla Thunderbird (en-US)Windows application

Affected:52.4.0Fixed in:52.4.0Mozilla

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityNone

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Exploit Intelligence

1.47%probability of exploitation in 30 days

71stpercentile

Elevated risk: more likely to be exploited than 71% of all known CVEs.

References

Patch1

bugzilla.mozilla.org

Vendor Advisory3

Third-Party Advisory8

Related Vulnerabilities

Other CWE-79 (Cross-Site Scripting (XSS)) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2020-11022	Medium	6.9	99%	-	Fix
CVE-2019-3929	Critical	9.8	99%	KEV	Fix
CVE-2020-9496	Medium	6.1	99%	-	-
CVE-2023-28341	Medium	6.1	99%	-	Fix
CVE-2018-12998	Medium	6.1	98%	-	-
CVE-2025-4123	High	7.6	98%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-11-25.