mistral-vibe: Improper Handling of Syntactically Invalid Structure
CVE-2026-87986 is a critical-severity improper handling of syntactically invalid structure vulnerability in mistral-vibe from Mistralai, with a CVSS 4.0 base score of 10.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected mistral-vibe versions: 1.3.4 and later. The record does not name a fixed version, so check the vendor advisory. 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.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of mistral-vibe you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on hiddenlayer.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Mistralai | mistral-vibe | 1.3.4 and later | Not stated |
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.
- Attack requirements
- NoneThe attack does not depend on a particular deployment or configuration.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Confidentiality (vulnerable system)
- HighSerious loss of confidentiality on the vulnerable system.
- Integrity (vulnerable system)
- HighSerious loss of integrity on the vulnerable system.
- Availability (vulnerable system)
- HighSerious loss of availability on the vulnerable system.
- Confidentiality (other systems)
- HighSerious loss of confidentiality on systems beyond the vulnerable one.
- Integrity (other systems)
- HighSerious loss of integrity on systems beyond the vulnerable one.
- Availability (other systems)
- HighSerious loss of availability on systems beyond the vulnerable one.
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. Scored by CNA.
Official description
An arbitrary code execution vulnerability in Mistral Vibe allows an attacker to bypass command permission checks using shell constructs it's parser cannot interpret. Unparsed portions are omitted from inspection, enabling embedded commands to execute on the user's system without approval.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Handling of Syntactically Invalid Structure
The product does not handle or incorrectly handles input that is not syntactically well-formed with respect to the associated specification.
More Improper Handling of Syntactically Invalid Structure vulnerabilities (CWE-228)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
References
Other vulnerabilities in mistral-vibe
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
Recent Improper Handling of Syntactically Invalid Structure vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 7.7 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 7.5 High severity
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