CVE-2026-71554

MEDIUMPre-NVD 5.35.3
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

Score 5.3 from GitHub Security Advisory (severity: MODERATE) published 2026-08-06. A secondary CVSS source baseline 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source

Also known asEUVD-2026-54177 (ENISA EUVD) · GHSA-6hr6-w5qg-qmwg (GitHub Security Advisories) · PYSEC-2026-3628 (OSV.dev)Source: ENISA EUVD

5.3EG
EchelonGraph verdictMonitorRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 5.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

h2 is a pure-Python implementation of a HTTP/2 protocol stack. Versions up to and including 4.4.0 accept request header blocks containing more than one Host header, and forward every Host header to the consuming application. Where the consumer downgrades HTTP/2 to HTTP/1.1, the resulting request carries two Host header lines, providing a request smuggling primitive. This issue is fixed in version 4.4.1.

CVSS v3
5.3
EG Score
5.3MEDIUMmedium confidence
EG Risk
39
EG Risk 39/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity53% × 45%
Impact severity (EG Severity): CVSS 5.3 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.4% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
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
0.4%
EPSS %ILE
36th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.3): severity, escalated by confirmed exploitation. This CVE's 5.3 is its impact severity (EG Severity), not escalated.

EG Severity
5.3 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track 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). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

August 6, 2026

Last Modified

October 24, 2026

Advisory Details (2)

Auto-updated Aug 6, 2026
Patch available. Sources: github_commit, github.
GitHub advisoryMentions a patch (unverified)

Duplicate Host header could facilitate request smuggling · Advisory · python-hyper/h2 · GitHub

Affected: v4.4.1

https://github.com/python-hyper/h2/security/advisories/GHSA-6hr6-w5qg-qmwg
GitHub commit

commit 292a40829fee (python-hyper/h2)

Fix landed in python-hyper/h2 commit 292a40829fee — awaiting tagged release

https://github.com/python-hyper/h2/commit/292a40829feefda98c8509dcdbbb4a57af9bd6a6

Vendor Advisories for CVE-2026-71554(1)

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

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
piph2 @ 4.4.1 (fixes <= 4.4.0)—ghsa

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

(5 across 5 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
python-h24.0.0-3 ... 4.3.0-2 (9 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
python-h24.1.0-4, 4.2.0-1, 4.3.0-1, 4.3.0-2
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
python-h24.2.0-1, 4.3.0-1, 4.3.0-2
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
python-h24.2.0-1, 4.3.0-1, 4.3.0-2
  • every version on: no fix on record
—
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
h20.1.0 ... 4.4.0 (47 versions)
  • every version up to 4.4.1: fixed in 4.4.1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 31× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed its CVE.org record (CNA or CISA ADP). An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 145 rows on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 45 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-13 16:57 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  2. 2026-11-12 16:34 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  3. 2026-11-11 16:40 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  4. 2026-11-10 16:45 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  5. 2026-11-09 16:36 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  6. 2026-11-08 16:40 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  7. 2026-11-07 16:39 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  8. 2026-11-06 16:39 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  9. 2026-11-05 16:38 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  10. 2026-11-04 16:36 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  11. 2026-11-03 16:49 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  12. 2026-11-02 16:46 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  13. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  14. 2026-11-01 07:39 UTCGHSA enrichmentGHSA-6hr6-w5qg-qmwg · GitHub severity MODERATE · GitHub CVSS 5.3
  15. 2026-11-01 07:39 UTCEchelonGraph re-scored
  16. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  17. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  18. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  19. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  20. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  21. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  22. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  23. 2026-10-25 14:07 UTCEchelonGraph re-scored
  24. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  25. 2026-10-23 21:32 UTCEchelonGraph re-scored
Show 75 more
  1. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  2. 2026-10-22 19:23 UTCEchelonGraph re-scored
  3. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  4. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  5. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  6. 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  7. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  8. 2026-10-18 03:17 UTCEchelonGraph re-scored
  9. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  10. 2026-10-16 16:44 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  11. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  12. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  13. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  14. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  15. 2026-10-12 15:42 UTCEchelonGraph re-scored
  16. 2026-10-11 19:28 UTCEchelonGraph re-scored
  17. 2026-10-11 16:43 UTCEchelonGraph re-scored
  18. 2026-10-11 14:03 UTCEchelonGraph re-scored
  19. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  20. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  21. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  22. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  23. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  24. 2026-10-06 23:21 UTCEchelonGraph re-scored
  25. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  26. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  27. 2026-10-05 08:20 UTCEchelonGraph re-scored
  28. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  29. 2026-10-04 05:46 UTCEchelonGraph re-scored
  30. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  31. 2026-10-02 09:36 UTCEchelonGraph re-scored
  32. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  33. 2026-09-30 22:58 UTCEchelonGraph re-scored
  34. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  35. 2026-09-29 05:51 UTCEchelonGraph re-scored
  36. 2026-09-27 17:13 UTCEchelonGraph re-scored
  37. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  38. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  39. 2026-09-25 04:18 UTCEchelonGraph re-scored
  40. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  41. 2026-09-23 16:13 UTCEchelonGraph re-scored
  42. 2026-09-22 14:19 UTCEchelonGraph re-scored
  43. 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  44. 2026-09-21 12:24 UTCEchelonGraph re-scored
  45. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  46. 2026-09-19 23:14 UTCEchelonGraph re-scored
  47. 2026-09-18 20:35 UTCEchelonGraph re-scored
  48. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  49. 2026-09-18 06:45 UTCEchelonGraph re-scored
  50. 2026-09-17 04:50 UTCEchelonGraph re-scored
  51. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  52. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  53. 2026-09-16 02:55 UTCEchelonGraph re-scored
  54. 2026-09-15 03:12 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  55. 2026-09-14 15:46 UTCEchelonGraph re-scored
  56. 2026-09-13 13:50 UTCEchelonGraph re-scored
  57. 2026-09-12 15:02 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  58. 2026-09-12 11:55 UTCEchelonGraph re-scored
  59. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  60. 2026-09-11 09:57 UTCEchelonGraph re-scored
  61. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  62. 2026-09-09 06:03 UTCEchelonGraph re-scored
  63. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  64. 2026-09-07 17:49 UTCEchelonGraph re-scored
  65. 2026-09-06 13:48 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  66. 2026-09-06 13:09 UTCEchelonGraph re-scored
  67. 2026-09-05 11:14 UTCEchelonGraph re-scored
  68. 2026-09-04 09:08 UTCEchelonGraph re-scored
  69. 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  70. 2026-09-03 06:09 UTCEchelonGraph re-scored
  71. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  72. 2026-09-02 00:48 UTCEchelonGraph re-scored
  73. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  74. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  75. 2026-08-31 22:31 UTCEchelonGraph re-scored

Frequently asked(5)

What is CVE-2026-71554?
CVE-2026-71554 is a medium-severity vulnerability; its CVE record was published on August 6, 2026. h2 is a pure-Python implementation of a HTTP/2 protocol stack. Versions up to and including 4.4.0 accept request header blocks containing more than one Host header, and forward every Host header to the consuming application. Where the consumer downgrades HTTP/2 to HTTP/1.1, the resulting request…
When was the CVE record for CVE-2026-71554 published?
The CVE record for CVE-2026-71554 was published on August 6, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 24, 2026; the record at its source may have been updated since.
Is CVE-2026-71554 actively exploited?
CVE-2026-71554 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (36th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-71554?
CVE-2026-71554 has a CVSS base score of 5.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-71554?
A fix for CVE-2026-71554 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-71554 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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