Security readout for executives and security teams
Plain-English summary
A flaw in Flarum before 1.8.16 lets someone holding an expired password-reset token bypass its 24-hour lifetime. They could change the associated account’s password and obtain an authenticated session. The attacker must already possess a valid but expired token.
Executive priority
Treat as an urgent account-compromise risk. Expedite upgrades for public Flarum deployments, prioritizing administrator and privileged-account exposure. There is no supplied evidence of active exploitation, but expired tokens may remain useful until remediation.
Technical view
The reset form checks token age, but SavePasswordController::handle() processes submitted tokens using PasswordToken::findOrFail() without expiry validation. Direct submission to the reset-processing endpoint therefore accepts an expired token. Flarum 1.8.16 contains the referenced correction.
Likely exposure
Internet-accessible Flarum installations running versions earlier than 1.8.16 are potentially exposed. Practical risk depends on whether an attacker possesses an expired reset token, which the CVSS assessment reflects as high attack complexity.
Exploitation context
The supplied record is not listed in KEV, and the cited material does not establish active exploitation. Exploitation is unauthenticated but requires access to a previously issued, expired password-reset token. Successful abuse can compromise the token’s associated account.
Researcher notes
The security boundary is inconsistent: expiry is enforced while rendering the reset form but omitted during password submission. Assessment should focus on server-side validation in the processing controller. The sources do not describe how attackers might obtain old tokens or confirm exploitation in the wild.
Mitigation direction
- Upgrade affected Flarum installations to version 1.8.16 or later.
- Follow the vendor release notes and referenced patch when implementing remediation.
- Investigate suspicious password changes and secure affected accounts if misuse is identified.
Validation and detection
- Inventory Flarum deployments and identify every instance running a version earlier than 1.8.16.
- Verify deployed packages and lockfiles show Flarum Framework 1.8.16 or later.
- Safely confirm the reset-processing path rejects tokens older than 24 hours after remediation.
- Review available logs for password resets involving unusually old tokens or unexpected session creation.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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CWE-324: Exact CWE lookup
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Open ATT&CK lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-39923 mapping review
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Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.2 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA and ADP enrichment extracted from CVE v5
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SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N——VulnCheckCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H2.25.9VulnCheckVulnerability scoring details
Base CVSS 4.0 score
9.2CriticalVector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Base CVSS 3.1 score
8.1HighVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
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ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- Release NotesCVE reference, VulnCheck · release-notes
- Pull RequestCVE reference, VulnCheck · issue-tracking
- Patch CommitCVE reference, VulnCheck · patch
- https://www.vulncheck.com/advisories/flarum-password-reset-token-expiry-bypass-via-post-resetCVE reference, VulnCheck · third-party-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.