Jupyter Server is the backend for Jupyter web applications. Prior to version 2.21.0, the 5xx request logging path in jupyter_server/log.py copies the Referer header into a JSON header block without applying the token scrubbing used for the request URI. A request that returns HTTP 500 while the Referer contains a token-bearing URL can therefore write that token to server logs in plaintext. An attacker who can read those logs can recover the token and use the affected user's Jupyter Server permissions. This issue is fixed in version 2.21.0.
CVE-2026-86049
“—” beside the score: it is equal to the CVSS score beside it.
Score 7.1 from GitHub Security Advisory (severity: HIGH) published 2026-09-17. A secondary CVSS source baseline 7.1; sources differ by 0.0.
Also known asEUVD-2026-82436 (ENISA EUVD) · GHSA-c3mw-737p-c7g2 (GitHub Security Advisories)Source: ENISA EUVD
- High severity, but no confirmed exploitation yet
A fix is available — apply it.
- CVSS v3
- 7.1
- EG Score
- 7.1HIGHmedium confidence
- EG Risk
- 32EG Risk 32/100
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)Severity71% × 45%Impact severity (EG Severity): CVSS 7.1 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.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
- 0.4%
- EPSS %ILE
- 35th
- 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 (7.1): severity, escalated by confirmed exploitation. This CVE's 7.1 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.1 HIGHCVSS-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; 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
September 17, 2026
Last Modified
September 24, 2026
Advisory Details (4)
Auto-updated Sep 17, 2026v2.21.0
Patch available: jupyter-server/jupyter_server v2.21.0
https://github.com/jupyter-server/jupyter_server/releases/tag/v2.21.0commit 52513529af70 (jupyter-server/jupyter_server)
Patch available: jupyter-server/jupyter_server v2.21.0 (contains commit 52513529af70)
https://github.com/jupyter-server/jupyter_server/commit/52513529af7096e622c00911b17627b266294717Fix referer token leak in server logs when the request causes a 500
Patch available: jupyter-server/jupyter_server v2.21.0 (PR #1681 merged 2026-07-20)
https://github.com/jupyter-server/jupyter_server/pull/16815xx request logging leaks token-bearing Referer header values · Advisory · jupyter-server/jupyter_server · GitHub
Affected: 2.21.0 by
https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-c3mw-737p-c7g2Vendor Advisories for CVE-2026-86049(3)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2026:87410Red Hat Product SecurityCritical
Red Hat Security Advisory: RHOAI 2.25.12 - Red Hat OpenShift AI
- RHSA-2026:84734Red Hat Product SecurityCritical
Red Hat Security Advisory: RHOAI 3.4.5 - Red Hat OpenShift AI
- GHSA-c3mw-737p-c7g2GitHub Security AdvisoriesHigh
Jupyter Server: 5xx request logging leaks token-bearing Referer header values
Patch Availability(3)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| redhat | rhoai/odh-feature-server-rhel9:1792148523 | 2026-10-21 | redhat |
| redhat | rhoai/odh-feature-server-rhel9:1791863220 | 2026-10-19 | redhat |
| pip | jupyter_server @ 2.21.0 (fixes <= 2.20.0) | — | 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
(4 across 4 ecosystems)
Debian:12(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| jupyter-server | 1.23.3-1 ... 2.9.1-1 (14 versions) |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| jupyter-server | 2.15.0-1, 2.17.0-1, 2.20.0-1, 2.20.0-2, 2.20.0-3 |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| jupyter-server | 2.15.0-1, 2.17.0-1, 2.20.0-1, 2.20.0-2, 2.20.0-3 |
| — |
PyPI(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| jupyter-server | 0.0.0 ... 2.9.1 (160 versions) |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 11× in last 7d / 50× 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.
- 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-11-01 07:38 UTCGHSA enrichmentGHSA-c3mw-737p-c7g2 · GitHub severity HIGH · GitHub CVSS 7.1
- 2026-11-01 07:38 UTCEG score recompute
- 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-10-27 19:06 UTCEG score recompute
- 2026-10-27 19:06 UTCVendor advisory
- 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-10-25 13:55 UTCEG score recompute
- 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-21 16:34 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-20 07:29 UTCEG score recompute
- 2026-10-20 07:29 UTCVendor advisory
- 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-18 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-18 03:05 UTCEG score recompute
- 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-16 16:44 UTCEPSS rescoreEPSS 0.4% · 34th percentile
Show 58 moreShow fewer
- 2026-10-15 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-14 16:34 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-10-13 05:23 UTCEG score recompute
- 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-10-12 14:52 UTCEG score recompute
- 2026-10-11 19:17 UTCEG score recompute
- 2026-10-11 16:34 UTCEG score recompute
- 2026-10-11 13:51 UTCEG score recompute
- 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-10-11 02:50 UTCEG score recompute
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-10-10 03:38 UTCEG score recompute
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-10-08 17:34 UTCEG score recompute
- 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-10-08 05:25 UTCEG score recompute
- 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-10-06 18:27 UTCEG score recompute
- 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-10-05 19:46 UTCEG score recompute
- 2026-10-05 17:44 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-10-05 08:26 UTCEG score recompute
- 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-10-03 22:20 UTCEG score recompute
- 2026-10-02 23:38 UTCEG score recompute
- 2026-10-02 17:57 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-10-02 00:10 UTCEG score recompute
- 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-10-01 01:28 UTCEG score recompute
- 2026-09-30 15:04 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-09-29 15:27 UTCEG score recompute
- 2026-09-29 04:04 UTCEG score recompute
- 2026-09-28 16:43 UTCEG score recompute
- 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-09-27 17:50 UTCEG score recompute
- 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-09-26 19:07 UTCEG score recompute
- 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-09-26 07:46 UTCEG score recompute
- 2026-09-24 21:24 UTCEG score recompute
- 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
- 2026-09-24 00:17 UTCEG score recompute
- 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.2% · 15th percentile
- 2026-09-23 01:37 UTCEG score recompute
- 2026-09-22 16:01 UTCEPSS rescoreEPSS 0.2% · 15th percentile
- 2026-09-22 02:55 UTCEG score recompute
- 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.2% · 15th percentile
- 2026-09-21 04:13 UTCEG score recompute
- 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.2% · 15th percentile
- 2026-09-19 18:10 UTCEG score recompute
- 2026-09-19 06:48 UTCEG score recompute
- 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 15th percentile
- 2026-09-18 19:28 UTCEG score recompute
- 2026-09-18 18:44 UTCEG score recompute
- 2026-09-17 21:20 UTCEG score recompute
- 2026-09-17 20:34 UTCEG score recomputeFirst assessed: 7.1 HIGH
- 2026-09-17 20:34 UTCMITRE cvelistV5first tracked
Related CVEs(same product + same vendor + same CWE)
Same product
10 shownDebian:12:jupyter-server
Same vendor
10 shownredhat:RHSA-2026:84734
Frequently asked(5)
What is CVE-2026-86049?
When was the CVE record for CVE-2026-86049 published?
Is CVE-2026-86049 actively exploited?
What is the CVSS score of CVE-2026-86049?
How do I remediate CVE-2026-86049?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-86049
Is Your Infrastructure Affected by CVE-2026-86049?
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