CVE-2020-17527

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 25% (97th 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
Trending — 3 sources updated this weekElevated
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 25%CVSS: 7.5Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

While investigating bug 64830 it was discovered that Apache Tomcat 10.0.0-M1 to 10.0.0-M9, 9.0.0-M1 to 9.0.39 and 8.5.0 to 8.5.59 could re-use an HTTP request header value from the previous stream received on an HTTP/2 connection for the request associated with the subsequent stream. While this would most likely lead to an error and the closure of the HTTP/2 connection, it is possible that information could leak between requests.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
65
EG Risk 65/100CISA 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
Severity75% × 45%
Exploitation40% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; 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
25%
EPSS %ILE
97th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; 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 (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). 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

December 3, 2020

Last Modified

October 8, 2026

Advisory Details (9)

Auto-updated Oct 8, 2026
Patch available.
generic

Pony Mail

https://lists.apache.org/thread.html/r9fd47f1b03e9b41d16a5cf72659b533887267d3398d963c2fff3abfa%40%3Ccommits.tomee.apache.org%3E
generic

Pony Mail

https://lists.apache.org/thread.html/ra35c8d617b17d59f400112cebadec43ad379f98198b4a9726190d7ee%40%3Cissues.guacamole.apache.org%3E
generic

Pony Mail

https://lists.apache.org/thread.html/rabbe6b3ae6a9795641d7a05c00d2378d5bbbe4240b7e20f09b092cce%40%3Cissues.guacamole.apache.org%3E
generic

oss-security - [SECURITY] CVE-2020-17527 Apache Tomcat HTTP/2 Request header mix-up

http://www.openwall.com/lists/oss-security/2020/12/03/3
generic

Pony Mail

https://lists.apache.org/thread.html/rce5ac9a40173651d540babce59f6f3825f12c6d4e886ba00823b11e5%40%3Cannounce.tomcat.apache.org%3E
generic

Pony Mail

https://lists.apache.org/thread.html/rd5babd13d7a350b369b2f647b4dd32ce678af42f9aba5389df1ae6ca%40%3Cusers.tomcat.apache.org%3E
generic

Pony Mail

https://lists.apache.org/thread.html/rce5ac9a40173651d540babce59f6f3825f12c6d4e886ba00823b11e5%40%3Cannounce.apache.org%3E
generic

Pony Mail

https://lists.apache.org/thread.html/raa0e9ad388c1e6fd1e301b5e080f9439f64cb4178119a86a4801cc53%40%3Cdev.tomcat.apache.org%3E
generic

Pony Mail

https://lists.apache.org/thread.html/r8a227ac6a755a6406c1cc47dd48800e973d4cf13fe7fe68ac59c679c%40%3Cdev.tomcat.apache.org%3E

Vendor Advisories for CVE-2020-17527(5)

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

Patch Availability(3)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntutomcat9-examples (9.0.31-1ubuntu0.2) @ focal2026-10-08ubuntu
redhattomcat2021-12-14redhat
redhatjws5-tomcat-native-0:1.2.25-3.redhat_3.el8jws2021-02-11redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(7 across 7 ecosystems)
Debian:10(1)
PackageVulnerable rangeFix by version rangeDependents
tomcat99.0.16-4 ... 9.0.31-1~deb10u2 (8 versions)
  • every version up to 9.0.31-1~deb10u3: fixed in 9.0.31-1~deb10u3
—
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
tomcat9—
  • every version up to 9.0.40-1: fixed in 9.0.40-1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
tomcat9—
  • every version up to 9.0.40-1: fixed in 9.0.40-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
tomcat9—
  • every version up to 9.0.40-1: fixed in 9.0.40-1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
tomcat9—
  • every version up to 9.0.40-1: fixed in 9.0.40-1
—
Debian:9(1)
PackageVulnerable rangeFix by version rangeDependents
tomcat88.5.14-1 ... 8.5.54-0+deb9u4 (41 versions)
  • every version up to 8.5.54-0+deb9u5: fixed in 8.5.54-0+deb9u5
—
Maven(1)
PackageVulnerable rangeFix by version rangeDependents
org.apache.tomcat:tomcat-coyote8.5.0 ... 8.5.9 (48 versions)
  • 10.0.0-M1 up to 10.0.0-M10: fixed in 10.0.0-M10
  • 9.0.0-M1 up to 9.0.40: fixed in 9.0.40
  • 8.5.0 up to 8.5.60: fixed in 8.5.60
—

Weakness Classification(1)

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

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 9× in last 7d / 31× 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 163 total refreshes for this CVE.

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

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 GitHub PoC). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCforse01/CVE-2020-17527-Tomcat
    First seen Feb 5, 2021
    Open source ↗

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2020-17527?
CVE-2020-17527 is a high vulnerability published on December 3, 2020. While investigating bug 64830 it was discovered that Apache Tomcat 10.0.0-M1 to 10.0.0-M9, 9.0.0-M1 to 9.0.39 and 8.5.0 to 8.5.59 could re-use an HTTP request header value from the previous stream received on an HTTP/2 connection for the request associated with the subsequent stream. While this…
When was CVE-2020-17527 disclosed?
CVE-2020-17527 was first published on December 3, 2020, with the most recent update on October 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2020-17527 actively exploited?
CVE-2020-17527 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 25% probability of exploitation in the next 30 days (97th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2020-17527?
CVE-2020-17527 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2020-17527?
A fix for CVE-2020-17527 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2020-17527 are linked in the Vendor Advisories panel on this page.

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