Is CVE-2017-7803 in the CISA KEV catalog?

No. CVE-2017-7803 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2017-7803?

CVE-2017-7803 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2017-7803?

CVE-2017-7803 has an EPSS score of 2.03% (79th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2017-7803?

Upgrade firefox on debian unstable to 55.0-1 or later. Fixes are available for 6 affected products.

CVE & CISA-KEV Catalog

CVE-2017-7803

HIGHEPSS 79th pctl

7.5

CVSS v3

NVD

Description

When a page's content security policy (CSP) header contains a "sandbox" directive, other directives are ignored. This results in the incorrect enforcement of CSP. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.

CWE-269Improper Privilege Management

How to fix

Remediation Available

firefoxDebian

Fixed in:55.0-1CVE-2017-7803

firefoxUbuntu

Fixed in:55.0.1+build2-0ubuntu0.14.04.2USN-3391-1

Fixed in:55.0.1+build2-0ubuntu0.16.04.2USN-3391-1

thunderbirdUbuntu

Fixed in:1:52.3.0+build1-0ubuntu0.14.04.1USN-3416-1

Fixed in:1:52.3.0+build1-0ubuntu0.16.04.1USN-3416-1

DeveloperEditionWindows application

Affected:52.3.0Fixed in:52.3.0Mozilla

Affected:55.0Fixed in:55.0Mozilla

Mozilla Firefox (en-US)Windows application

Affected:55.0Fixed in:55.0Mozilla

Affected:52.3.0Fixed in:52.3.0Mozilla

Mozilla Thunderbird (en-US)Windows application

Affected:52.3.0Fixed in:52.3.0Mozilla

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 InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityHigh

AvailabilityNone

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

Exploit Intelligence

2.03%probability of exploitation in 30 days

79thpercentile

Elevated risk: more likely to be exploited than 79% of all known CVEs.

References

Patch1

bugzilla.mozilla.org

Vendor Advisory3

Third-Party Advisory7

Related Vulnerabilities

Other CWE-269 (Improper Privilege Management) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2017-12635	Critical	9.8	100%	-	Fix
CVE-2022-24637	Critical	9.8	99%	-	Fix
CVE-2017-5689	Critical	9.8	92%	KEV	Fix
CVE-2020-3243	Critical	9.8	88%	-	-
CVE-2024-21888	High	8.8	87%	-	-
CVE-2022-0441	Critical	9.8	85%	-	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.