What is CVE-2026-42608?
Grav is a file-based Web platform. Prior to 2.0.0-beta.2, there is a Path Traversal vulnerability within the FormFlash core component. By manipulating the session_id (passed as __form-flash-id in POST requests), an unauthenticated attacker can traverse the filesystem to create arbitrary directories and write an index.yaml file containing attacker-controlled data. This vulnerability can lead to unauthorized modification of application behavior, potential data integrity issues, and service disruption in production environments. This vulnerability is fixed in 2.0.0-beta.2.
The record classifies CVE-2026-42608 under weakness class CWE-22. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 147 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 9.1 — CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - CVSS v4.0 base score
- 8.8
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P - EPSS (FIRST)
- 0.5% probability of exploitation in the next 30 days, higher than 41.9% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 8.2/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-05-11
Is CVE-2026-42608 being exploited?
Weaponised exploit code for CVE-2026-42608 is publicly available. 1 public proof-of-concept repository is tracked for this identifier.
- trickest/cve (trickest)
Affected products and versions
- getgrav: grav
Affected software packages:
composer:getgrav/grav— patched in 2.0.0-beta.2
How to fix CVE-2026-42608
Fixed versions are recorded for 1 package: composer:getgrav/grav 2.0.0-beta.2. Vendor advisory: https://github.com/getgrav/grav/security/advisories/GHSA-hmcx-ch82-3fv2. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2026-42608
1 tracked threat in the Threadlinqs corpus references CVE-2026-42608, either in the campaign’s CVE list or as an indicator on the campaign record.
Sources
Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.