CVE-2020-5247

MEDIUMNVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.5 under NVD CVSS v3. EPSS exploit probability: 2.5% (84th percentile of EPSS-scored CVEs). 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
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 2.5%CVSS: 6.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

In Puma (RubyGem) before 4.3.2 and before 3.12.3, if an application using Puma allows untrusted input in a response header, an attacker can use newline characters (i.e. CR, LF or/r, /n) to end the header and inject malicious content, such as additional headers or an entirely new response body. This vulnerability is known as HTTP Response Splitting. While not an attack in itself, response splitting is a vector for several other attacks, such as cross-site scripting (XSS). This is related to CVE-2019-16254, which fixed this vulnerability for the WEBrick Ruby web server. This has been fixed in versions 4.3.2 and 3.12.3 by checking all headers for line endings and rejecting headers with those characters.

CVSS v3
6.5
EG Score
6.5MEDIUMmedium confidence
EG Risk
35
EG Risk 35/100CISA SSVC

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
Severity65% × 45%
Exploitation3% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track or Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
2.5%
EPSS %ILE
84th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track or Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

February 28, 2020

Last Modified

November 21, 2024

References (14)

Vendor Advisories for CVE-2020-5247(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(6 across 6 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
puma—
  • every version up to 3.12.4-1: fixed in 3.12.4-1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
puma—
  • every version up to 3.12.4-1: fixed in 3.12.4-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
puma—
  • every version up to 3.12.4-1: fixed in 3.12.4-1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
puma—
  • every version up to 3.12.4-1: fixed in 3.12.4-1
—
Debian:9(1)
PackageVulnerable rangeFix by version rangeDependents
puma3.6.0-1, 3.6.0-1+deb9u1
  • every version up to 3.6.0-1+deb9u2: fixed in 3.6.0-1+deb9u2
—
RubyGems(1)
PackageVulnerable rangeFix by version rangeDependents
puma4.0.0 ... 4.3.1 (8 versions)
  • every version up to 3.12.4: fixed in 3.12.4
  • 4.0.0 up to 4.3.3: fixed in 4.3.3
—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 25× 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 172 total refreshes for this CVE.

  1. 2026-10-09 20:04 UTCEPSS rescore
  2. 2026-10-08 16:39 UTCEPSS rescore
  3. 2026-10-07 23:44 UTCEPSS rescore
  4. 2026-10-06 15:13 UTCEPSS rescore
  5. 2026-10-05 17:40 UTCEPSS rescore
  6. 2026-10-04 23:18 UTCEPSS rescore
  7. 2026-10-03 14:22 UTCEPSS rescore
  8. 2026-10-03 14:22 UTCEPSS rescore
  9. 2026-10-02 16:22 UTCEPSS rescore
  10. 2026-10-01 19:46 UTCEPSS rescore
  11. 2026-09-30 15:20 UTCEG score recompute
  12. 2026-09-30 14:59 UTCEPSS rescore
  13. 2026-09-27 13:41 UTCEPSS rescore
  14. 2026-09-27 08:32 UTCOSV refresh
  15. 2026-09-26 15:54 UTCEPSS rescore
  16. 2026-09-26 15:54 UTCEPSS rescore
  17. 2026-09-26 00:21 UTCEPSS rescore
  18. 2026-09-22 14:44 UTCEPSS rescore
  19. 2026-09-21 20:28 UTCEPSS rescore
  20. 2026-09-19 15:37 UTCEPSS rescore
  21. 2026-09-18 19:23 UTCEPSS rescore
  22. 2026-09-17 19:22 UTCEPSS rescore
  23. 2026-09-16 14:04 UTCEPSS rescore
  24. 2026-09-15 03:06 UTCEPSS rescore
  25. 2026-09-12 14:57 UTCEPSS rescore
Show 75 more
  1. 2026-09-08 21:56 UTCEPSS rescore
  2. 2026-09-07 17:51 UTCOSV refresh
  3. 2026-09-07 15:58 UTCEPSS rescore
  4. 2026-09-06 13:44 UTCEPSS rescore
  5. 2026-09-05 15:25 UTCEPSS rescore
  6. 2026-09-04 13:57 UTCEPSS rescore
  7. 2026-09-04 13:57 UTCEPSS rescore
  8. 2026-09-04 05:03 UTCEPSS rescore
  9. 2026-09-02 14:08 UTCEPSS rescore
  10. 2026-09-01 03:32 UTCEPSS rescore
  11. 2026-08-30 19:14 UTCEPSS rescore
  12. 2026-08-30 01:19 UTCEPSS rescore
  13. 2026-08-28 21:37 UTCEPSS rescore
  14. 2026-08-27 14:21 UTCEPSS rescore
  15. 2026-08-26 14:42 UTCEPSS rescore
  16. 2026-08-21 23:45 UTCEPSS rescore
  17. 2026-08-21 03:23 UTCOSV refresh
  18. 2026-08-19 17:00 UTCEPSS rescore
  19. 2026-08-18 13:44 UTCEPSS rescore
  20. 2026-08-17 13:43 UTCEPSS rescore
  21. 2026-08-17 13:43 UTCEPSS rescore
  22. 2026-08-16 14:52 UTCEPSS rescore
  23. 2026-08-16 02:11 UTCEPSS rescore
  24. 2026-08-15 01:27 UTCEPSS rescore
  25. 2026-08-13 21:57 UTCEPSS rescore
  26. 2026-08-12 13:47 UTCEPSS rescore
  27. 2026-08-08 16:33 UTCEPSS rescore
  28. 2026-08-07 16:23 UTCEPSS rescore
  29. 2026-08-06 13:43 UTCEPSS rescore
  30. 2026-08-05 19:14 UTCEPSS rescore
  31. 2026-08-05 18:41 UTCOSV refresh
  32. 2026-08-04 15:06 UTCEPSS rescore
  33. 2026-08-04 10:34 UTCEPSS rescore
  34. 2026-08-02 02:24 UTCEPSS rescore
  35. 2026-08-01 04:12 UTCEPSS rescore
  36. 2026-07-30 16:25 UTCEPSS rescore
  37. 2026-07-30 01:27 UTCEPSS rescore
  38. 2026-07-28 15:33 UTCEPSS rescore
  39. 2026-07-26 14:52 UTCEPSS rescore
  40. 2026-07-25 14:15 UTCEPSS rescore
  41. 2026-07-24 14:15 UTCEPSS rescore
  42. 2026-07-23 14:15 UTCEPSS rescore
  43. 2026-07-23 01:54 UTCEG score recompute
  44. 2026-07-22 22:40 UTCEG score recompute
  45. 2026-07-22 14:05 UTCEPSS rescore
  46. 2026-07-21 15:22 UTCEPSS rescore
  47. 2026-07-21 15:22 UTCEPSS rescore
  48. 2026-07-20 17:04 UTCEPSS rescore
  49. 2026-07-20 17:04 UTCEPSS rescore
  50. 2026-07-19 18:18 UTCOSV refresh
  51. 2026-07-19 14:28 UTCEPSS rescore
  52. 2026-07-19 14:28 UTCEPSS rescore
  53. 2026-07-19 02:26 UTCEPSS rescore
  54. 2026-07-19 02:26 UTCEPSS rescore
  55. 2026-07-18 10:02 UTCEPSS rescore
  56. 2026-07-16 17:00 UTCEPSS rescore
  57. 2026-07-15 16:55 UTCEPSS rescore
  58. 2026-07-15 16:55 UTCEPSS rescore
  59. 2026-07-15 01:57 UTCEPSS rescore
  60. 2026-07-13 22:27 UTCEPSS rescore
  61. 2026-07-13 22:27 UTCEPSS rescore
  62. 2026-07-13 06:10 UTCEPSS rescore
  63. 2026-07-13 06:10 UTCEPSS rescore
  64. 2026-07-12 05:44 UTCEPSS rescore
  65. 2026-07-12 05:44 UTCEPSS rescore
  66. 2026-07-11 08:25 UTCEPSS rescore
  67. 2026-07-11 08:25 UTCEPSS rescore
  68. 2026-07-09 19:07 UTCEPSS rescore
  69. 2026-07-08 15:12 UTCEPSS rescore
  70. 2026-07-07 13:43 UTCEPSS rescore
  71. 2026-07-06 16:25 UTCEPSS rescore
  72. 2026-07-06 02:21 UTCEPSS rescore
  73. 2026-07-06 02:21 UTCEPSS rescore
  74. 2026-07-05 02:28 UTCEPSS rescore
  75. 2026-07-05 02:28 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2020-5247?
CVE-2020-5247 is a medium vulnerability published on February 28, 2020. In Puma (RubyGem) before 4.3.2 and before 3.12.3, if an application using Puma allows untrusted input in a response header, an attacker can use newline characters (i.e. CR, LF or/r, /n) to end the header and inject malicious content, such as additional headers or an entirely new response body. This…
When was CVE-2020-5247 disclosed?
CVE-2020-5247 was first published on February 28, 2020, 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-2020-5247 actively exploited?
CVE-2020-5247 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 2.5% probability of exploitation in the next 30 days (84th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2020-5247?
CVE-2020-5247 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2020-5247?
A fix for CVE-2020-5247 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2020-5247 are linked in the Vendor Advisories panel on this page.

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