Serendipity: Missing Critical Step in Authentication
CVE-2026-67351 is a high-severity missing critical step in authentication vulnerability in Serendipity from S9y, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists version 2.6.1 as the first without the flaw, so updating Serendipity to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.56% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Serendipity to 2.6.1 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| S9y | Serendipity | before 2.6.1 | 2.6.1 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.7 | High | CNA (vulncheck.com) |
| CVSS 3.1 | 8.8 | High | CNA (vulncheck.com) |
Official description
Serendipity before 2.6.1 contains an authentication context confusion vulnerability where password validation and session loading operate independently without ensuring both use the same user record. An authenticated Editor can create a username collision with an Administrator account and obtain administrative privileges by logging in with their own password while the session loads the Administrator's account data.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Missing Critical Step in Authentication
The product implements an authentication technique, but it skips a step that weakens the technique.
More Missing Critical Step in Authentication vulnerabilities (CWE-304)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in Serendipity
- 8.5 High severity
- 7.2 High severity
- 8.8 High severity
Recent Missing Critical Step in Authentication vulnerabilities
- 7.3 High severity
- 7.3 High severity
- 8.1 High severity
- 7.3 High severity
- 9.8 Critical severity
- 7.2 High severity
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