Security readout for executives and security teams
Plain-English summary
Craft CMS has a race condition that can let a valid limited-use impersonation link be used more times than intended. The attacker must already have a non-expired impersonation URL and overcome any rate limiting. Business risk is unauthorized access as a more privileged user if such a token is exposed.
Executive priority
Prioritize remediation during the next security update window, faster for admin-heavy Craft CMS deployments or environments using impersonation links. The issue is not broadly exploitable without a valid token, but a successful case could enable privileged access.
Technical view
CVE-2026-27128 affects Craft CMS 4.5.0-RC1 through 4.16.18 and 5.0.0-RC1 through 5.8.22. The token service getTokenRoute() checks token usage and updates usage in separate non-atomic operations, creating a TOCTOU condition for explicitly limited-use tokens. Patched in 4.16.19 and 5.8.23.
Likely exposure
Exposure is limited to Craft CMS installations in the affected version ranges that use limited-use impersonation tokens. Practical impact depends on whether attackers can obtain a valid, non-expired impersonation URL for a higher-privileged account.
Exploitation context
No active exploitation is indicated in the provided sources, and the CVE is not listed as KEV. Exploitation requires prior possession of a valid impersonation URL, concurrent request timing, and bypassing any rate-limiting rules in place.
Researcher notes
Key constraint is prerequisite access to a valid, non-expired impersonation URL. The flaw is a non-atomic usage check/update sequence in token validation. The public fix commit and GitHub advisory are the primary technical references; evidence does not support claims of public exploitation.
Mitigation direction
- Upgrade Craft CMS 4.x to 4.16.19 or later.
- Upgrade Craft CMS 5.x to 5.8.23 or later.
- Review vendor advisory and release guidance before deployment.
- Ensure rate-limiting controls around token-backed routes remain enabled and monitored.
- Review handling and sharing of impersonation URLs.
Validation and detection
- Inventory Craft CMS instances and record exact versions.
- Confirm no instance runs 4.5.0-RC1 through 4.16.18.
- Confirm no instance runs 5.0.0-RC1 through 5.8.22.
- Check whether impersonation URLs are used in your environment.
- Review logs for unusual repeated use of limited-use impersonation tokens.
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
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CWE-367: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
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 lookupPrivilege behavior lookup
The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupDatabase behavior lookup
The CVE wording references database injection or access, so collection and exfiltration review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-27128 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.9 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe 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:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
6.9MediumVector: CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/craftcms/cms/security/advisories/GHSA-6fx5-5cw5-4897CVE reference · x_refsource_CONFIRM
- https://github.com/craftcms/cms/commit/3e4afe18279951c024c64896aa2b93cda6d95fdfCVE reference · x_refsource_MISC
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.
Time-of-check Time-of-use (TOCTOU) Race Condition
Time-of-check Time-of-use (TOCTOU) Race Condition represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.