CVE-2026-100635

MEDIUMPre-NVD 5.95.9
EchelonGraph scoreMEDIUM confidence

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

Score 5.9 from GitHub Security Advisory (severity: HIGH) published 2026-09-26. The CNA's CVSS baseline 5.9; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: the CNA's CVSS, EPSS, GitHub Security Advisory
Trending — 3 sources updated this weekElevated

Also known asEUVD-2026-87729 (ENISA EUVD) · GHSA-9f49-xx3h-chx9 (GitHub Security Advisories)Source: ENISA EUVD

5.9EG
EchelonGraph verdictPlan mitigationNo release containing the referenced fix is confirmed: check the referenced fix and the vendor's advisory for a release that contains it; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule (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: 0.3%CVSS: 5.9Exploit: No code on recordExposed services: Not assessed

A fix is referenced (a reference tagged "Patch", often a source commit), but no release containing it is confirmed — find the release that contains it; until it is applied, mitigate (WAF / firewall / segmentation).

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
5.9MEDIUMmedium confidence
EG Risk
43
EG Risk 43/100

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)
Severity59% × 45%
Impact severity (EG Severity): CVSS 5.9 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 or medium mission impact; Track* at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable no (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 referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule.
EPSS PROB
0.3%
EPSS %ILE
25th
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 (5.9): severity, escalated by confirmed exploitation. This CVE's 5.9 is its impact severity (EG Severity), not escalated.

EG Severity
5.9 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.3% 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 or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says. In the directive's words, “Fix on system upgrade” means that, “unless conditions change”, the vulnerability “should be remediated the next time the vulnerable asset receives a scheduled major upgrade or rebuild”: its timelines are “dynamic as facts change”, and a KEV listing shortens them.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 referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (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)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says. In the directive's words, “Fix on system upgrade” means that, “unless conditions change”, the vulnerability “should be remediated the next time the vulnerable asset receives a scheduled major upgrade or rebuild”: its timelines are “dynamic as facts change”, and a KEV listing shortens them.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (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

September 26, 2026

Last Modified

October 27, 2026

Advisory Details (4)

Auto-updated Sep 26, 2026
Fix referenced — no release confirmed yet. Sources: github, github_commit.
Web page

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 advisoryMentions a patch (unverified)

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 9× in last 7d / 61× 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. 2026-11-01 16:33 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  2. 2026-10-31 16:31 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  3. 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  4. 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  5. 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  6. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  7. 2026-10-27 01:43 UTCEG score recompute
  8. 2026-10-27 01:43 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  9. 2026-10-26 16:30 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  10. 2026-10-26 15:32 UTCEG score recompute
  11. 2026-10-26 15:32 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  12. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  13. 2026-10-25 15:58 UTCEG score recompute
  14. 2026-10-24 16:31 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  15. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  16. 2026-10-23 09:53 UTCEG score recompute
  17. 2026-10-23 09:53 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  18. 2026-10-22 16:33 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  19. 2026-10-21 16:31 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  20. 2026-10-20 16:31 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  21. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  22. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  23. 2026-10-18 05:11 UTCEG score recompute
  24. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  25. 2026-10-16 16:40 UTCEPSS rescoreEPSS 0.3% · 16th percentile
Show 61 more
  1. 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  2. 2026-10-14 16:31 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  3. 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  4. 2026-10-12 16:41 UTCEG score recompute
  5. 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  6. 2026-10-11 20:16 UTCEG score recompute
  7. 2026-10-11 18:29 UTCEG score recompute
  8. 2026-10-11 15:02 UTCEG score recompute
  9. 2026-10-11 13:47 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  10. 2026-10-11 12:04 UTCEG score recompute
  11. 2026-10-11 12:04 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  12. 2026-10-10 19:59 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  13. 2026-10-10 13:37 UTCEG score recompute
  14. 2026-10-10 13:37 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  15. 2026-10-09 20:06 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  16. 2026-10-09 15:14 UTCEG score recompute
  17. 2026-10-09 15:14 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  18. 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  19. 2026-10-08 16:33 UTCEG score recompute
  20. 2026-10-08 16:33 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  21. 2026-10-08 15:38 UTCEG score recompute
  22. 2026-10-08 15:38 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  23. 2026-10-08 03:42 UTCEG score recompute
  24. 2026-10-08 03:42 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  25. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  26. 2026-10-07 05:19 UTCEG score recompute
  27. 2026-10-07 05:19 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  28. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  29. 2026-10-06 06:56 UTCEG score recompute
  30. 2026-10-06 06:56 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  31. 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  32. 2026-10-05 08:33 UTCEG score recompute
  33. 2026-10-05 08:33 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  34. 2026-10-04 23:21 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  35. 2026-10-04 10:10 UTCEG score recompute
  36. 2026-10-04 10:10 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  37. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  38. 2026-10-03 11:47 UTCEG score recompute
  39. 2026-10-03 11:47 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  40. 2026-10-02 13:21 UTCEG score recompute
  41. 2026-10-02 13:21 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  42. 2026-10-01 19:49 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  43. 2026-10-01 14:58 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  44. 2026-09-30 16:36 UTCEG score recompute
  45. 2026-09-30 16:36 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  46. 2026-09-30 15:02 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  47. 2026-09-29 18:14 UTCEG score recompute
  48. 2026-09-29 18:14 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  49. 2026-09-29 15:20 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  50. 2026-09-28 19:32 UTCEG score recompute
  51. 2026-09-28 19:31 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  52. 2026-09-28 19:02 UTCEG score recompute
  53. 2026-09-28 19:02 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  54. 2026-09-28 13:50 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  55. 2026-09-28 11:19 UTCEG score recompute
  56. 2026-09-28 11:19 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  57. 2026-09-27 12:57 UTCEG score recompute
  58. 2026-09-27 12:57 UTCGHSA enrichmentGHSA-9f49-xx3h-chx9 · GitHub severity HIGH · GitHub CVSS 5.9
  59. 2026-09-26 14:34 UTCEG score recompute
  60. 2026-09-26 13:40 UTCEG score recomputeFirst assessed: 5.9 MEDIUM
  61. 2026-09-26 13:30 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-100635?
CVE-2026-100635 is a medium-severity vulnerability; its CVE record was 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 made public?
CVE-2026-100635 was made public on September 11, 2026: that is the date its CVE record's CNA, VulnCheck, gives for when the vulnerability was made public. The CVE record itself was published on September 26, 2026. EchelonGraph's copy of the record carries a last-modified date of October 27, 2026; the record at its source may have been updated since.
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 (25th 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 (the CNA's own assessment, by vulncheck; NVD's own analysis pending).
How do I remediate CVE-2026-100635?
A fix for CVE-2026-100635 is referenced (a reference tagged "Patch", often a source commit), but EchelonGraph has no release containing it on record. Check that reference and the vendor's advisory for a release that contains the fix and update to it; until then, restrict network exposure of the affected system or apply the vendor's mitigation. The vendor advisories EchelonGraph has for CVE-2026-100635 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-100635

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