CVE-2026-49400

LOWPre-NVD 3.33.3
EchelonGraph scoreMEDIUM confidence

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

Score 3.3 from GitHub Security Advisory (severity: LOW) published 2026-09-14. A secondary CVSS source baseline 3.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
Trending — 4 sources updated this week

Also known asEUVD-2026-77682 (ENISA EUVD) · GHSA-2ff2-mx52-q8wp (GitHub Security Advisories)Source: ENISA EUVD

3.3EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 3.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

October System provides the system module for October Content Management System. Prior to versions 3.7.17 and 4.2.21, the backend SessionMaker trait stored widget session state as base64(serialize(...)) and consumed it with unserialize() without an allowed_classes restriction. Any code path that could write to a widget.* session key with attacker-controlled bytes could trigger PHP object injection the next time the widget read its session state, allowing instantiation of arbitrary classes and reachable PHP gadget chains. This issue only affects installations running with cms.safe_mode enabled. Safe Mode is a niche opt-in feature, primarily used for demo installations and multi-tenant or shared-editor scenarios where untrusted users are deliberately granted access to the CMS markup editor. In standard production deployments Safe Mode is off, backend access is restricted to trusted administrators, and a markup editor can already execute arbitrary PHP directly. The session-write path that reaches this sink is gated by the Safe Mode sandbox, so installations without Safe Mode enabled are not exposed. Scope of impact is narrow even with Safe Mode enabled. The standard backend code paths that populate widget session state (search terms, sort options, selected IDs, filter values) wrap the input inside a known array shape before serializing, so user-supplied values never reach unserialize() as a controllable serialized payload. Exploitation requires the Safe Mode session-write path together with a suitable PHP gadget chain reachable from the installed dependency set. The hardening below removes the underlying object-injection sink so the class of issue is closed off regardless. The vulnerability has been patched in v3.7.17 and v4.2.21. Two changes were applied. Backend\Traits\SessionMaker now stores widget session state as plain JSON instead of base64(serialize(...)), eliminating the object-injection sink entirely for new writes. Reads transparently fall back to the legacy format for one upgrade cycle so existing sessions retain their saved widget state. The legacy unserialize() fallback path now sets allowed_classes => false, so even values written before the upgrade cannot instantiate objects. As a workaround, restrict CMS markup editing access to fully trusted administrators only, the standard October CMS recommendation for any deployment.

CVSS v3
3.3
EG Score
3.3LOWmedium confidence
EG Risk
15
EG Risk 15/100

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)
Severity33% × 45%
Impact severity (EG Severity): CVSS 3.3 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.2% × 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 every mission impact level.
Exploitation none (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 available. Apply it within your standard update timelines.
EPSS PROB
0.2%
EPSS %ILE
14th
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 (3.3): severity, escalated by confirmed exploitation. This CVE's 3.3 is its impact severity (EG Severity), not escalated.

EG Severity
3.3 LOWCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.2% 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 every mission impact level.CISA BOD 26-04: 60 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 every mission impact level.

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

Exploitation none (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.

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 14, 2026

Last Modified

September 30, 2026

References (1)

Vendor Advisories for CVE-2026-49400(1)

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

Patch Availability(2)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
composeroctober/system @ 3.7.17 (fixes < 3.7.17)—ghsa
composeroctober/system @ 4.2.23 (fixes >= 4.0.0, < 4.2.23)—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

(1 across 1 ecosystem)
Packagist(1)
PackageVulnerable rangeFix by version rangeDependents
october/systemv1.0.319 ... v1.1.9 (169 versions)
  • every version up to 3.7.17: fixed in 3.7.17
  • 4.0.0 up to 4.2.23: fixed in 4.2.23
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 43× 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 16:34 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  2. 2026-11-01 07:46 UTCGHSA enrichmentGHSA-2ff2-mx52-q8wp · GitHub severity LOW · GitHub CVSS 3.3
  3. 2026-11-01 07:46 UTCEG score recompute
  4. 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  5. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  6. 2026-10-29 17:47 UTCEG score recompute
  7. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  8. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  9. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  10. 2026-10-27 06:25 UTCOSV refresh
  11. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  12. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  13. 2026-10-25 14:22 UTCEG score recompute
  14. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  15. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  16. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  17. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  18. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  19. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  20. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  21. 2026-10-18 03:34 UTCEG score recompute
  22. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  23. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  24. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  25. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
Show 39 more
  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  2. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  3. 2026-10-12 16:00 UTCEG score recompute
  4. 2026-10-11 19:43 UTCEG score recompute
  5. 2026-10-11 16:57 UTCEG score recompute
  6. 2026-10-11 14:21 UTCEG score recompute
  7. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  8. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  9. 2026-10-09 20:08 UTCEG score recompute
  10. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  11. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  12. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  13. 2026-10-06 19:30 UTCEG score recompute
  14. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  15. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  16. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  17. 2026-10-03 18:52 UTCEG score recompute
  18. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  19. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  20. 2026-09-30 18:09 UTCEG score recompute
  21. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  22. 2026-09-28 20:16 UTCEG score recompute
  23. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  24. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  25. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  26. 2026-09-26 00:27 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  27. 2026-09-25 19:39 UTCEG score recompute
  28. 2026-09-23 17:53 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  29. 2026-09-22 18:11 UTCEG score recompute
  30. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  31. 2026-09-19 17:34 UTCEG score recompute
  32. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  33. 2026-09-16 16:56 UTCEG score recompute
  34. 2026-09-16 15:36 UTCEG score recompute
  35. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  36. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  37. 2026-09-14 18:32 UTCEG score recompute
  38. 2026-09-14 17:21 UTCEG score recomputeFirst assessed: 3.3 LOW
  39. 2026-09-14 17:21 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-49400?
CVE-2026-49400 is a low-severity vulnerability; its CVE record was published on September 14, 2026. October System provides the system module for October Content Management System. Prior to versions 3.7.17 and 4.2.21, the backend SessionMaker trait stored widget session state as base64(serialize(...)) and consumed it with unserialize() without an allowed_classes restriction. Any code path that…
When was the CVE record for CVE-2026-49400 published?
The CVE record for CVE-2026-49400 was published on September 14, 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 September 30, 2026; the record at its source may have been updated since.
Is CVE-2026-49400 actively exploited?
CVE-2026-49400 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (14th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-49400?
CVE-2026-49400 has a CVSS base score of 3.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-49400?
A fix for CVE-2026-49400 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-49400 are linked in the Vendor Advisories panel on this page.

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