CVE-2021-31810

Exp

An issue was discovered in Ruby through 2.6.7, 2.7.x through 2.7.3, and 3.x through 3.0.1. A malicious FTP server can use the PASV response to trick Net::FTP into connecting back to a given IP address and port. This potentially makes curl extract information about services that are otherwise private and not disclosed (e.g., the attacker can conduct port scans and service banner extractions).

Published: 2021-07-13 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-31810 is rated High Exploit Risk (70.6/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 3.05%). 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +2.38% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-31810

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-31810

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.67% 3.05% +2.38%
2 2026-06-04 0.58% 0.67% +0.09%
3 2026-03-04 — 0.58% —

Full EPSS history (68 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-31810

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.8 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:P/I:N/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-31810

OS Trackers for CVE-2021-31810

vendor priority summary link
alpine — CVE-2021-31810: 1 source package rows (ruby); 49 state rows across 9 repos (3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 9, open 40. https://security.alpinelinux.org/vuln/CVE-2021-31810
debian not yet assigned CVE-2021-31810 not yet assigned priority: Debian including 2 source packages (jruby, ruby2.7), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-31810
gentoo normal CVE-2021-31810: 1 GLSA(s) (202401-27), 1 atom(s) (dev-lang/ruby); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-31810
redhat medium — https://access.redhat.com/security/cve/CVE-2021-31810
suse high CVE-2021-31810 severity important: SUSE including 361 source package names (2.17-17.3:libruby2_5-2_5-2.5.9-4.20.1, 2.17-17.3:ruby2.5-2.5.9-4.20.1, …), 1144 product×package rows across 262 product lines (Container bci/ruby, Container suse/rmt-server, … (262 product lines)): Fixed 981, Known Affected 160, Known Not Affected 3. https://www.suse.com/security/cve/CVE-2021-31810/
ubuntu low CVE-2021-31810 low priority: Ubuntu including 5 source packages (ruby1.9.1, ruby2.0, ruby2.3, ruby2.5, ruby2.7), 44 status rows across 9 suites (bionic, focal, groovy, hirsute, impish, jammy, trusty, upstream, xenial): DNE 33, released 6, needs-triage 5. https://ubuntu.com/security/CVE-2021-31810

Affected software / configurations for CVE-2021-31810

Vendor Product Version Raw CPE
ruby-lang ruby <= 2.6.7 cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*
ruby-lang ruby >= 2.7.0, <= 2.7.3 cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*
ruby-lang ruby >= 3.0.0, <= 3.0.1 cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
oracle jd_edwards_enterpriseone_tools < 9.2.6.1 cpe:2.3:a:oracle:jd_edwards_enterpriseone_tools:*:*:*:*:*:*:*:*

References for CVE-2021-31810

cvelogic Threat Intelligence