CVE-2026-105798

HIGHPre-NVD 8.78.7
EchelonGraph scoreMEDIUM confidence

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

This high-severity CVE scores 8.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (40th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Elevated

Also known asEUVD-2026-93427 (ENISA EUVD)Source: ENISA EUVD

8.7EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 8.7Exploit: No code on recordExposed services: Not assessed

The CVE record names the fixed release — apply it.

SimpleChat is a secure AI conversation application with personal and group workspaces for document-grounded interactions. Prior to 0.261.029, POST /api/group_documents/upload stores an attacker-controlled group document filename that group_workspaces.html later interpolates into inline Share event handlers. The escapeGroupHtml function leaves apostrophes unchanged, while escapeHtml produces an HTML entity that the browser decodes before JavaScript evaluation, so either path permits the filename to terminate the handler string. An authenticated group Owner, Admin, or DocumentManager can persist script that executes in the SimpleChat origin when another group member clicks Share, allowing access to victim-visible data and actions with the victim session. This issue is fixed in version 0.261.029.

CVSS v3
8.7
EG Score
8.7HIGHmedium confidence
EG Risk
55
EG Risk 55/100

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)
Severity87% × 45%
Impact severity (EG Severity): CVSS 8.7 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (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: The CVE record names the fixed release. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.5%
EPSS %ILE
40th
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 (8.7): severity, escalated by confirmed exploitation. This CVE's 8.7 is its impact severity (EG Severity), not escalated.

EG Severity
8.7 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
EG Likelihood
0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-26). 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, Track* at medium and Attend at high mission impact.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, Track* at medium and Attend at high mission impact.

The CVE record names the fixed release. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (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

October 6, 2026

Last Modified

October 6, 2026

Advisory Details (2)

Auto-updated Oct 6, 2026
Fix named in the CVE record. Sources: github, github_commit.
GitHub commit

commit 537a259eb048 (microsoft/simplechat)

Fix landed in microsoft/simplechat commit 537a259eb048 — awaiting tagged release

https://github.com/microsoft/simplechat/commit/537a259eb048b8f6d1c94193fa0c9683ab0bace9
GitHub advisoryMentions a patch (unverified)

Stored XSS via group document filename in inline onclick handler · Advisory · microsoft/simplechat · GitHub

https://github.com/microsoft/simplechat/security/advisories/GHSA-qwcw-r653-j8c6

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 42× 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.

  1. 2026-11-02 16:43 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  2. 2026-11-01 16:33 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  3. 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  4. 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  5. 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  6. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  7. 2026-10-27 11:07 UTCEG score recompute
  8. 2026-10-26 16:30 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  9. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  10. 2026-10-25 14:55 UTCEG score recompute
  11. 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  12. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  13. 2026-10-22 16:33 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  14. 2026-10-21 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  15. 2026-10-20 16:31 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  16. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  17. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  18. 2026-10-18 05:08 UTCEG score recompute
  19. 2026-10-17 19:33 UTCEG score recompute
  20. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  21. 2026-10-16 16:40 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  22. 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  23. 2026-10-14 16:31 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  24. 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  25. 2026-10-12 16:39 UTCEG score recompute
Show 17 more
  1. 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  2. 2026-10-11 19:33 UTCEG score recompute
  3. 2026-10-11 18:27 UTCEG score recompute
  4. 2026-10-11 15:00 UTCEG score recompute
  5. 2026-10-11 13:47 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  6. 2026-10-10 21:07 UTCEG score recompute
  7. 2026-10-10 19:59 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  8. 2026-10-09 22:38 UTCEG score recompute
  9. 2026-10-09 20:06 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  10. 2026-10-08 23:39 UTCEG score recompute
  11. 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  12. 2026-10-08 01:16 UTCEG score recompute
  13. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  14. 2026-10-06 15:31 UTCEG score recompute
  15. 2026-10-06 14:55 UTCEG score recompute
  16. 2026-10-06 14:30 UTCEG score recomputeFirst assessed: 8.7 HIGH
  17. 2026-10-06 14:29 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-105798?
CVE-2026-105798 is a high-severity vulnerability; its CVE record was published on October 6, 2026. SimpleChat is a secure AI conversation application with personal and group workspaces for document-grounded interactions. Prior to 0.261.029, POST /api/group_documents/upload stores an attacker-controlled group document filename that group_workspaces.html later interpolates into inline Share event…
When was the CVE record for CVE-2026-105798 published?
The CVE record for CVE-2026-105798 was published on October 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 6, 2026; the record at its source may have been updated since.
Is CVE-2026-105798 actively exploited?
CVE-2026-105798 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (40th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-105798?
CVE-2026-105798 has a CVSS base score of 8.7 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-105798?
The CVE record for CVE-2026-105798 names the fix: "This issue is fixed in version 0.261.029."

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