HOMEVULNERABILITIESCVE-2021-3311
CRITICAL

CVE-2021-3311

CWE-613Published: February 5, 2021· Updated: Jun 17, 2026

9.8
CVSS v3.1

Official Description

An issue was discovered in October through build 471. It reactivates an old session ID (which had been invalid after a logout) once a new login occurs. NOTE: this violates the intended Auth/Manager.php authentication behavior but, admittedly, is only relevant if an old session ID is known to an attacker.

NVD Source

Technical Analysis

CVE-2021-3311 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

octobercms1 product(s)
october
Source: NVD CPE · 1 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://github.com/octobercms/library/commit/642f597489e6f644d4bd9a0c267e864cabead024
PATCHhttps://github.com/octobercms/library/commit/642f597489e6f644d4bd9a0c267e864cabead024
ADVISORYhttps://anisiosantos.me/october-cms-token-reactivation
ADVISORYhttps://octobercms.com/forum/chan/announcements
ADVISORYhttps://anisiosantos.me/october-cms-token-reactivation
ADVISORYhttps://octobercms.com/forum/chan/announcements

All References (6)

→
https://anisiosantos.me/october-cms-token-reactivationExploit · Third Party Advisory
→
https://github.com/octobercms/library/commit/642f597489e6f644d4bd9a0c267e864cabead024Patch · Third Party Advisory
→
https://octobercms.com/forum/chan/announcementsVendor Advisory
→
https://anisiosantos.me/october-cms-token-reactivationExploit · Third Party Advisory
→
https://github.com/octobercms/library/commit/642f597489e6f644d4bd9a0c267e864cabead024Patch · Third Party Advisory
→
https://octobercms.com/forum/chan/announcementsVendor Advisory

Quick Facts

CVE IDCVE-2021-3311
CVSS Score9.8 / 10
SeverityCRITICAL
WeaknessCWE-613
CISA KEVNo
Affected1 vendor(s)
PublishedFeb 5, 2021

Related CVEs (CWE-613)

CVE-2021-25992
9.8
CVE-2026-1435
9.8
CVE-2025-4528
9.8
CVE-2025-40566
9.8
CVE-2026-26342
9.8
CVE-2026-26290
9.8

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-3311 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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