CVE-2017-7783
If a long user name is used in a username/password combination in a site URL (such as " http://UserName:Password@example.com"), the resulting modal prompt will hang in a non-responsive state or crash, causing a denial of service.
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 13.8%, higher than 97% of all known CVEs. Patch or mitigate before the next change window.
Description
If a long user name is used in a username/password combination in a site URL (such as " http://UserName:Password@example.com"), the resulting modal prompt will hang in a non-responsive state or crash, causing a denial of service. This vulnerability affects Firefox < 55.
- CVSS 3.0
- 7.5 HIGHCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 13.85% probability · 97th percentile
- Public exploits
- 1 in Exploit-DB · verified · first 20 October 2017
- CISA KEV
- Not listed
- Weakness
- CWE-20
- Affected
- mozilla/firefox
- Source
- security@mozilla.org
EPSS moved from 10.3% on 21 September 2026 to 13.8% on 27 October 2026, peaking at 14.1% on 22 September 2026. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”.
Public exploits (1)
Entries in Exploit-DB that cite this CVE. Links go to the Exploit-DB page and to the file in the public repository; nothing is hosted here. A verified tick means the Exploit-DB team confirmed the exploit works against the stated version.
References
- http://www.securityfocus.com/bid/100401Third Party Advisory, VDB Entry
- http://www.securitytracker.com/id/1039124Third Party Advisory, VDB Entry
- https://bugzilla.mozilla.org/show_bug.cgi?id=1360842Exploit, Issue Tracking, Patch
- https://www.exploit-db.com/exploits/43020/Third Party Advisory, VDB Entry
- https://www.mozilla.org/security/advisories/mfsa2017-18/Vendor Advisory
- http://www.securityfocus.com/bid/100401Third Party Advisory, VDB Entry
- http://www.securitytracker.com/id/1039124Third Party Advisory, VDB Entry
- https://bugzilla.mozilla.org/show_bug.cgi?id=1360842Exploit, Issue Tracking, Patch
- https://www.exploit-db.com/exploits/43020/Third Party Advisory, VDB Entry
- https://www.mozilla.org/security/advisories/mfsa2017-18/Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.