CVE-2021-41084

HIGHNVD 8.78.7—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.7 under NVD CVSS v3. EPSS exploit probability: 1.2%, top 34% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this week
8.7
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 8.7Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

http4s is an open source scala interface for HTTP. In affected versions http4s is vulnerable to response-splitting or request-splitting attacks when untrusted user input is used to create any of the following fields: Header names (Header.nameå), Header values (Header.value), Status reason phrases (Status.reason), URI paths (Uri.Path), URI authority registered names (URI.RegName) (through 0.21). This issue has been resolved in versions 0.21.30, 0.22.5, 0.23.4, and 1.0.0-M27 perform the following. As a matter of practice http4s services and client applications should sanitize any user input in the aforementioned fields before returning a request or response to the backend. The carriage return, newline, and null characters are the most threatening.

CVSS v3
8.7
EG Score
8.7(medium)
EG Risk
44(Track)
EG Risk 44/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity87% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
65.9%
KEV
Not listed

Published

September 21, 2021

Last Modified

November 21, 2024

References (8)

Affected Packages

(9 across 1 ecosystem)
Maven(9)
PackageVulnerable rangeFixed inDependents
org.http4s:http4s-client_2.120.23.0, 0.23.1, 0.23.2, 0.23.30.23.4—
org.http4s:http4s-client_2.130.23.0, 0.23.1, 0.23.2, 0.23.30.23.4—
org.http4s:http4s-client_30.23.0, 0.23.1, 0.23.2, 0.23.30.23.4—
org.http4s:http4s-server_2.100.10.0 ... 0.9.3 (131 versions)——
org.http4s:http4s-server_2.110.10.0 ... 0.9.3 (220 versions)——
org.http4s:http4s-server_2.120.23.0, 0.23.1, 0.23.2, 0.23.30.23.4—
org.http4s:http4s-server_2.130.23.0, 0.23.1, 0.23.2, 0.23.30.23.4—
org.http4s:http4s-server_2.13.0-M50.20.0 ... 0.20.9 (12 versions)——
org.http4s:http4s-server_30.23.0, 0.23.1, 0.23.2, 0.23.30.23.4—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 50× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 105 total refreshes for this CVE.

  1. 2026-07-23 02:04 UTCEG score recompute
  2. 2026-07-22 22:50 UTCEG score recompute
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Frequently asked(5)

What is CVE-2021-41084?
CVE-2021-41084 is a high vulnerability published on September 21, 2021. http4s is an open source scala interface for HTTP. In affected versions http4s is vulnerable to response-splitting or request-splitting attacks when untrusted user input is used to create any of the following fields: Header names (Header.nameå), Header values (Header.value), Status reason phrases…
When was CVE-2021-41084 disclosed?
CVE-2021-41084 was first published in the National Vulnerability Database on September 21, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-41084 actively exploited?
CVE-2021-41084 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 65.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-41084?
CVE-2021-41084 has a CVSS v3 base score of 8.7 (NVD).
How do I remediate CVE-2021-41084?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-41084, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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