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CVE-2017-7783

42
FAUCET Score

CVE-2017-7783 describes a denial-of-service vulnerability in Mozilla Firefox versions prior to 55. This flaw allows an attacker to crash or render Firefox unresponsive by crafting a malicious URL containing an excessively long username in the username/password combination. Rated as HIGH severity (CVSS 7.5), this vulnerability can be exploited remotely without user interaction, leading to application unavailability. While not listed on the KEV catalog, public exploit code exists (EDB-43020), though there is minimal community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 55.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
< 55CPE match
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

7.5HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.0

Exploit Intelligence

EPSS Score
13.70%
Probability of exploitation in next 30 days
EPSS Percentile
96.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
ExploitDB: EDB-43020 · Oct 20, 2017
This CVE's current EPSS score of 0.1370 is in the 94th percentile among its peer group of 51,485 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

mozillapatch availablevia nvd_reference
View patch

Vendor Advisories (1)

redhatCVE-2017-7783Low

Mozilla: DOS attack through long username in URL (MFSA 2017-18)

Aug 8, 2017

References

bugzilla.mozilla.org / show_bug.cgi
ExploitIssue TrackingPatch
exploit-db.com / exploits/43020
Third Party AdvisoryVDB Entry
mozilla.org / security/advisories/mfsa2017-18
Vendor Advisory
securityfocus.com / bid/100401
Third Party AdvisoryVDB Entry
securitytracker.com / id/1039124
Third Party AdvisoryVDB Entry