CVE-2023-27539

There is a denial of service vulnerability in the header parsing component of Rack.

Published: 2025-01-08 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-27539 is rated Moderate Risk (42.9/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.06%). 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-2023-27539

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 0.36% 1.06% +0.70%
2 2026-04-29 0.34% 0.36% +0.03%
3 2026-04-11 — 0.34% —

Full EPSS history (29 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-27539

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L 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:N)
Data isn’t meaningfully altered or forged.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 3.9 1.4 [email protected]
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
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 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2023-27539

GitHub Security Advisory for CVE-2023-27539

GHSA-c6qg-cjj8-47qp · Severity: low · Ecosystem: rubygems — Possible Denial of Service Vulnerability in Rack's header parsing

OS Trackers for CVE-2023-27539

vendor priority summary link
debian not yet assigned CVE-2023-27539 not yet assigned priority: Debian including 1 source packages (ruby-rack), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2023-27539
redhat medium — https://access.redhat.com/security/cve/CVE-2023-27539
suse medium — https://www.suse.com/security/cve/CVE-2023-27539/
ubuntu medium CVE-2023-27539 medium priority: Ubuntu including 1 source packages (ruby-rack), 12 status rows across 12 suites (bionic, focal, jammy, kinetic, lunar, mantic, noble, oracular, plucky, trusty, upstream, xenial): released 7, not-affected 3, ignored 2. https://ubuntu.com/security/CVE-2023-27539

Affected software / configurations for CVE-2023-27539

Vendor Product Version Raw CPE
rack rack >= 2.0.0, < 2.2.6.4 cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
rack rack >= 3.0.0, < 3.0.6.1 cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
debian debian_linux 11.0 cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*

References for CVE-2023-27539

cvelogic Threat Intelligence