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CVE-2021-3311

31
FAUCET Score

CVE-2021-3311 affects October CMS, specifically builds up to 471, by reactivating a previously invalidated session ID upon a new user login. This critical vulnerability (CVSS 9.8) allows an unauthenticated attacker to potentially gain full control over the system (confidentiality, integrity, and availability) with low attack complexity, provided they know an old session ID. Despite its high severity, there is currently no public exploit code available, it is not listed on the KEV catalog, and it has received minimal community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
<= 1.0.471CPE matchmatch criteria
cpe:2.3:a:octobercms:october:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.90%
Probability of exploitation in next 30 days
EPSS Percentile
85.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0290 is in the 76th percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

composerpatch availablevia ghsa
Product: october/rainFixed in: 1.0.472
composerpatch availablevia ghsa
Product: october/rainFixed in: 1.1.2
github_advisorypatch availablevia nvd_reference
View patch

Vendor Advisories (1)

composerGHSA-7ggw-h8pp-r95rcritical

October CMS Session ID not invalidated after logout

Feb 10, 2021

References

anisiosantos.me / october-cms-token-reactivation
ExploitThird Party Advisory
github.com / octobercms/library/commit/642f597489e6f644d4bd9a0c267e864cabead024
PatchThird Party Advisory
octobercms.com / forum/chan/announcements
Vendor Advisory