CVE-2026-100635

MEDIUMPre-NVD 5.95.9—
EchelonGraph scoreHIGH confidence

Score 5.9 from GitHub Security Advisory (severity: HIGH) published 2026-09-26. A secondary CVSS source baseline 5.9; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this weekElevated
5.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.9Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

SiYuan before v3.8.4 contains an authentication bypass vulnerability in the publish service where session cookies are issued without Secure or SameSite attributes over plaintext HTTP connections. An on-path attacker can observe a valid publish-visitor-session-id cookie from a Basic Auth exchange and replay it to access authenticated publish endpoints without knowing the account password.

CVSS v3
5.9
EG Score
5.9MEDIUMhigh confidence
EG Risk
43
EG Risk 43/100CISA 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
Severity59% × 45%
Exploitation40% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
15th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* at high (mission-essential systems).

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

Exploitation public PoC (CISA Vulnrichment) · Automatable no (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

September 26, 2026

Last Modified

September 28, 2026

Advisory Details (4)

Auto-updated Sep 26, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_commit.
generic

SiYuan before v3.8.4 Authentication Bypass via Plaintext Session Cookie | Advisories | VulnCheck

https://www.vulncheck.com/advisories/siyuan-before-3.8.4-authentication-bypass-via-plaintext-session-cookie
github_commit

commit ff4d215f78a8 (siyuan-note/siyuan)

Fix landed in siyuan-note/siyuan commit ff4d215f78a8 — awaiting tagged release

https://github.com/siyuan-note/siyuan/commit/ff4d215f78a8d6e6db6052be18b5f9f4db9c7d68
github_commit

commit 79d47867b106 (siyuan-note/siyuan)

Fix landed in siyuan-note/siyuan commit 79d47867b106 — awaiting tagged release

https://github.com/siyuan-note/siyuan/commit/79d47867b106467c951475a9193455b48d1f3682
github Patch Available🟡 PoC Available

Plaintext Publish Session Cookie Enables Authentication Bypass · Advisory · siyuan-note/siyuan · GitHub

https://github.com/siyuan-note/siyuan/security/advisories/GHSA-7j37-4gq6-wm7m

Vendor Advisories for CVE-2026-100635(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 22× in last 7d / 27× 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.

  1. 2026-10-04 10:10 UTCEG score recompute
  2. 2026-10-04 10:10 UTCGHSA enrichment
  3. 2026-10-03 14:25 UTCEPSS rescore
  4. 2026-10-03 11:47 UTCEG score recompute
  5. 2026-10-03 11:47 UTCGHSA enrichment
  6. 2026-10-02 13:21 UTCEG score recompute
  7. 2026-10-02 13:21 UTCGHSA enrichment
  8. 2026-10-01 19:49 UTCEPSS rescore
  9. 2026-10-01 14:58 UTCGHSA enrichment
  10. 2026-09-30 16:36 UTCEG score recompute
  11. 2026-09-30 16:36 UTCGHSA enrichment
  12. 2026-09-30 15:02 UTCEPSS rescore
  13. 2026-09-29 18:14 UTCEG score recompute
  14. 2026-09-29 18:14 UTCGHSA enrichment
  15. 2026-09-29 15:20 UTCEPSS rescore
  16. 2026-09-28 19:32 UTCEG score recompute
  17. 2026-09-28 19:31 UTCGHSA enrichment
  18. 2026-09-28 19:02 UTCEG score recompute
  19. 2026-09-28 19:02 UTCGHSA enrichment
  20. 2026-09-28 13:50 UTCEPSS rescore
  21. 2026-09-28 11:19 UTCEG score recompute
  22. 2026-09-28 11:19 UTCGHSA enrichment
  23. 2026-09-27 12:57 UTCEG score recompute
  24. 2026-09-27 12:57 UTCGHSA enrichment
  25. 2026-09-26 14:34 UTCEG score recompute
Show 2 more
  1. 2026-09-26 13:40 UTCEG score recompute
  2. 2026-09-26 13:30 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-100635?
CVE-2026-100635 is a medium vulnerability published on September 26, 2026. SiYuan before v3.8.4 contains an authentication bypass vulnerability in the publish service where session cookies are issued without Secure or SameSite attributes over plaintext HTTP connections. An on-path attacker can observe a valid publish-visitor-session-id cookie from a Basic Auth exchange…
When was CVE-2026-100635 disclosed?
CVE-2026-100635 was first published on September 26, 2026, with the most recent update on September 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-100635 actively exploited?
CVE-2026-100635 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (15th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-100635?
CVE-2026-100635 has a CVSS base score of 5.9 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-100635?
A fix for CVE-2026-100635 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-100635 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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