CVE-2020-25613

An issue was discovered in Ruby through 2.5.8, 2.6.x through 2.6.6, and 2.7.x through 2.7.1. WEBrick, a simple HTTP server bundled with Ruby, had not checked the transfer-encoding header value rigorously. An attacker may potentially exploit this issue to bypass a reverse proxy (which also has a poor header check), which may lead to an HTTP Request Smuggling attack.

Published: 2020-10-06 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-25613 is rated Moderate Risk (64.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 3.80%). EPSS rose +3.53% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

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

Exploit prediction scoring system (EPSS) score for CVE-2020-25613

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 0.27% 3.80% +3.53%
2 2026-01-29 0.20% 0.27% +0.07%
3 2026-01-24 — 0.20% —

Full EPSS history (30 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-25613

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:P/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:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2020-25613

GitHub Security Advisory for CVE-2020-25613

GHSA-gwfg-cqmg-cf8f · Severity: high · Ecosystem: rubygems — WEBRick vulnerable to HTTP Request/Response Smuggling

OS Trackers for CVE-2020-25613

vendor priority summary link
alpine — CVE-2020-25613: 1 source package rows (ruby); 40 state rows across 10 repos (3.10-main, 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 10, open 30. https://security.alpinelinux.org/vuln/CVE-2020-25613
debian not yet assigned CVE-2020-25613 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-2020-25613
gentoo normal CVE-2020-25613: 1 GLSA(s) (202401-27), 1 atom(s) (dev-lang/ruby); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2020-25613
redhat medium — https://access.redhat.com/security/cve/CVE-2020-25613
suse medium CVE-2020-25613 severity moderate: SUSE including 313 source package names (2.17-17.3:libruby2_5-2_5-2.5.8-4.14.1, 2.17-17.3:ruby2.5-2.5.8-4.14.1, …), 1059 product×package rows across 255 product lines (Container bci/ruby, Container suse/rmt-server, … (255 product lines)): Fixed 913, Known Affected 135, Will Not Fix 6, Known Not Affected 5. https://www.suse.com/security/cve/CVE-2020-25613/
ubuntu low CVE-2020-25613 low priority: Ubuntu including 5 source packages (ruby1.9.1, ruby2.0, ruby2.3, ruby2.5, ruby2.7), 30 status rows across 6 suites (bionic, focal, groovy, trusty, upstream, xenial): DNE 21, released 5, needs-triage 4. https://ubuntu.com/security/CVE-2020-25613

Affected software / configurations for CVE-2020-25613

Vendor Product Version Raw CPE
ruby-lang ruby <= 2.5.8 cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*
ruby-lang ruby >= 2.6.0, <= 2.6.6 cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*
ruby-lang ruby >= 2.7.0, <= 2.7.1 cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*
ruby-lang webrick <= 1.6.0 cpe:2.3:a:ruby-lang:webrick:*:*:*:*:*:ruby:*:*
fedoraproject fedora 32 cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*

References for CVE-2020-25613

cvelogic Threat Intelligence