CVE-2026-28367

CRITICALNVD 9.19.1
EchelonGraph scoreMEDIUM confidence

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

This critical-severity CVE scores 9.1 under NVD CVSS v3. EPSS exploit probability: 0.7% (53rd percentile of EPSS-scored CVEs). GitHub Security Advisory CVSS 8.7 is lower than this score; a lower GitHub score revises it only when its advisory is newer than the CVE record's last change, and this advisory (published 2026-03-27) is not newer than that change (2026-10-30), so it does not.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3
Trending — 4 sources updated this week

Also known asEUVD-2026-16694 (ENISA EUVD) · GHSA-3gv6-g396-9v4r (GitHub Security Advisories)Source: ENISA EUVD

9.1EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.7%CVSS: 9.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

A flaw was found in Undertow. A remote attacker can exploit this vulnerability by sending \r\r\r as a header block terminator. This can be used for request smuggling with certain proxy servers, such as older versions of Apache Traffic Server and Google Cloud Classic Application Load Balancer, potentially leading to unauthorized access or manipulation of web requests.

CVSS v3
9.1
EG Score
9.1CRITICALmedium confidence
EG Risk
41
EG Risk 41/100

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)
Severity91% × 45%
Impact severity (EG Severity): CVSS 9.1 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.7% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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.
EPSS PROB
0.7%
EPSS %ILE
53rd
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 (9.1): severity, escalated by confirmed exploitation. This CVE's 9.1 is its impact severity (EG Severity), not escalated.

EG Severity
9.1 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
0.7% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-01). 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; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade 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; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (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

March 27, 2026

Last Modified

October 30, 2026

Advisory Details (4)

Auto-updated Sep 16, 2026
Patch available. Sources: redhat.
Red HatMentions a patch (unverified)

2443260 – (CVE-2026-28367) CVE-2026-28367 undertow: Undertow: Request smuggling via `\r\r\r` as a header block terminator

https://bugzilla.redhat.com/show_bug.cgi?id=2443260
Red HatMentions a patch (unverified)

CVE-2026-28367 - Red Hat Customer Portal

Affected: Red Hat Enterprise Linux 8 or OpenShift Container Platform 4, is affected by this vulnerability and a fix may be released to a

https://access.redhat.com/security/cve/CVE-2026-28367
Red HatMentions a patch (unverified)
https://access.redhat.com/errata/RHSA-2026:25126
Red HatMentions a patch (unverified)
https://access.redhat.com/errata/RHSA-2026:25125

Vendor Advisories for CVE-2026-28367(3)

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
redhatio.undertow/undertow-core:2.3.24.SP2-redhat-000012026-06-10redhat
redhateap8-wildfly-0:8.1.6-7.GA_redhat_00010.1.el9eap2026-06-10redhat
mavenio.undertow:undertow-parent—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

(2 across 2 ecosystems)
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
undertow1.3.11-1 ... 2.3.8-2 (56 versions)
  • every version on: no fix on record
—
Maven(1)
PackageVulnerable rangeFix by version rangeDependents
io.undertow:undertow-parent1.0.0.Alpha1 ... 2.3.9.Final (336 versions)
  • every version through 2.3.23.Final: no fix on record
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 30× in last 7d / 101× 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 it from the CNA feed. 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). Most recent first.

Showing the most recent 100 of 372 refreshes 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 272 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-02 10:09 UTCEG score recompute
  2. 2026-11-02 10:09 UTCVendor advisory
  3. 2026-11-02 10:09 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  4. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  5. 2026-11-01 07:53 UTCEG score recompute
  6. 2026-11-01 07:53 UTCVendor advisory
  7. 2026-11-01 07:53 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  8. 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  9. 2026-10-31 05:39 UTCEG score recompute
  10. 2026-10-31 05:39 UTCVendor advisory
  11. 2026-10-31 05:39 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  12. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  13. 2026-10-30 03:26 UTCVendor advisory
  14. 2026-10-30 03:26 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  15. 2026-10-30 02:45 UTCEG score recompute
  16. 2026-10-30 02:45 UTCVendor advisory
  17. 2026-10-30 02:45 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  18. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  19. 2026-10-29 11:42 UTCEG score recompute
  20. 2026-10-29 11:42 UTCVendor advisory
  21. 2026-10-29 11:42 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  22. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  23. 2026-10-28 09:30 UTCEG score recompute
  24. 2026-10-28 09:30 UTCVendor advisory
  25. 2026-10-28 09:29 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
Show 75 more
  1. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  2. 2026-10-27 06:32 UTCEG score recompute
  3. 2026-10-27 06:32 UTCVendor advisory
  4. 2026-10-27 06:31 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  5. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  6. 2026-10-26 00:26 UTCEG score recompute
  7. 2026-10-26 00:26 UTCVendor advisory
  8. 2026-10-26 00:26 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  9. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  10. 2026-10-25 14:38 UTCEG score recompute
  11. 2026-10-24 23:16 UTCEG score recompute
  12. 2026-10-24 23:16 UTCVendor advisory
  13. 2026-10-24 23:16 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  14. 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.9% · 60th percentile
  15. 2026-10-23 21:03 UTCEG score recompute
  16. 2026-10-23 21:03 UTCVendor advisory
  17. 2026-10-23 21:03 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  18. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  19. 2026-10-22 18:49 UTCEG score recompute
  20. 2026-10-22 18:49 UTCVendor advisory
  21. 2026-10-22 18:49 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  22. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  23. 2026-10-21 16:33 UTCEG score recompute
  24. 2026-10-21 16:33 UTCVendor advisory
  25. 2026-10-21 16:33 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  26. 2026-10-21 16:32 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  27. 2026-10-20 16:32 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  28. 2026-10-20 14:16 UTCEG score recompute
  29. 2026-10-20 14:16 UTCVendor advisory
  30. 2026-10-20 14:16 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  31. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  32. 2026-10-19 12:01 UTCEG score recompute
  33. 2026-10-19 12:01 UTCVendor advisory
  34. 2026-10-19 12:00 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  35. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  36. 2026-10-18 09:46 UTCVendor advisory
  37. 2026-10-18 09:46 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  38. 2026-10-18 03:50 UTCEG score recompute
  39. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  40. 2026-10-17 02:33 UTCEG score recompute
  41. 2026-10-17 02:33 UTCVendor advisory
  42. 2026-10-17 02:33 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  43. 2026-10-16 16:41 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  44. 2026-10-16 00:19 UTCEG score recompute
  45. 2026-10-16 00:19 UTCVendor advisory
  46. 2026-10-16 00:18 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  47. 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  48. 2026-10-14 17:29 UTCVendor advisory
  49. 2026-10-14 17:29 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  50. 2026-10-14 16:46 UTCEG score recompute
  51. 2026-10-14 16:46 UTCVendor advisory
  52. 2026-10-14 16:45 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  53. 2026-10-14 16:32 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  54. 2026-10-14 13:19 UTCEG score recompute
  55. 2026-10-14 13:19 UTCVendor advisory
  56. 2026-10-14 13:19 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  57. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  58. 2026-10-13 11:04 UTCEG score recompute
  59. 2026-10-13 11:04 UTCVendor advisory
  60. 2026-10-13 11:03 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  61. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  62. 2026-10-12 16:16 UTCEG score recompute
  63. 2026-10-12 08:48 UTCVendor advisory
  64. 2026-10-12 08:48 UTCGHSA enrichmentGHSA-3gv6-g396-9v4r · GitHub severity HIGH · GitHub CVSS 8.7
  65. 2026-10-11 19:59 UTCEG score recompute
  66. 2026-10-11 17:12 UTCEG score recompute
  67. 2026-10-11 14:42 UTCEG score recompute
  68. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  69. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  70. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  71. 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  72. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  73. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.9% · 58th percentile
  74. 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.9% · 57th percentile
  75. 2026-10-04 23:21 UTCEPSS rescoreEPSS 0.9% · 57th percentile

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Frequently asked(5)

What is CVE-2026-28367?
CVE-2026-28367 is a critical-severity vulnerability; its CVE record was published on March 27, 2026. A flaw was found in Undertow. A remote attacker can exploit this vulnerability by sending \r\r\r as a header block terminator. This can be used for request smuggling with certain proxy servers, such as older versions of Apache Traffic Server and Google Cloud Classic Application Load Balancer,…
When was CVE-2026-28367 made public?
CVE-2026-28367 was made public on August 27, 2025: that is the date its CVE record's CNA, Red Hat, Inc., gives for when the vulnerability was made public. The CVE record itself was published on March 27, 2026. EchelonGraph's copy of the record carries a last-modified date of October 30, 2026; the record at its source may have been updated since.
Is CVE-2026-28367 actively exploited?
CVE-2026-28367 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.7% probability of exploitation in the next 30 days (53rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-28367?
CVE-2026-28367 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2026-28367?
A fix for CVE-2026-28367 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-28367 are linked in the Vendor Advisories panel on this page.

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