MEDIUM
CVE-2021-3851
CWE-601Published: October 19, 2021· Updated: Jun 17, 2026
5.4
CVSS v3.1
Official Description
firefly-iii is vulnerable to URL Redirection to Untrusted Site
Technical Analysis
CVE-2021-3851 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.
CVSS v3.1 Vector Breakdown
Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.Low
User InteractionRequired
ScopeChanged
Impact
ConfidentialityLow
IntegrityLow
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Affected Vendors & Products
firefly-iii1 product(s)
firefly iii
Source: NVD CPE · 1 total CPE entries
Exploit & PoC Resources
NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.
Official Patches & Advisories
All References (4)
→
https://github.com/firefly-iii/firefly-iii/commit/8662dfa4c0f71efef61c31dc015c6f723db8318dPatch · Third Party Advisory
→
https://huntr.dev/bounties/549a1040-9b5e-420b-9b80-20700dd9d592Exploit · Patch · Third Party Advisory
→
https://github.com/firefly-iii/firefly-iii/commit/8662dfa4c0f71efef61c31dc015c6f723db8318dPatch · Third Party Advisory
→
https://huntr.dev/bounties/549a1040-9b5e-420b-9b80-20700dd9d592Exploit · Patch · Third Party Advisory
Quick Facts
CVE IDCVE-2021-3851
CVSS Score5.4 / 10
SeverityMEDIUM
WeaknessCWE-601
CISA KEVNo
Affected1 vendor(s)
PublishedOct 19, 2021
Related CVEs (CWE-601)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-3851 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.