CVE-2026-87986: Mistral Vibe arbitrary code execution via shell syntax parsing bypass

CVE-2026-87986 · Severity: info · CVSS 10 · Published 2026-09-11

Mistral Vibe is a command execution tool that checks and approves shell commands before running them. An attacker can exploit a parser limitation to hide unauthorized commands inside shell syntax that Vibe's parser cannot understand, causing those commands to execute without user approval. This allows arbitrary code execution on systems using Vibe for command authorization.

Technologies: Mistral Vibe. Vendors: Mistral.

Quick answers

Is CVE-2026-87986 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-87986 being exploited in the wild.
How severe is CVE-2026-87986?
Informational severity, with a CVSS score of 10, published 11 September 2026.
Which products and versions are affected?
Mistral Vibe v1.3.4 and later.
Is there a fix for CVE-2026-87986?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-87986 attacked?
It is attacked over the network.
Am I affected by CVE-2026-87986?
Check whether you run Mistral Vibe at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability stems from improper handling of syntactically invalid shell constructs in Vibe's command parser (CWE-228). Vibe uses tree-sitter-bash to parse shell commands for authorization checks, but when the parser encounters unsupported Bash or Zsh syntax, it wraps it in ERROR nodes and continues. The find_commands() function only extracts commands from successfully parsed nodes, missing executable content hidden in ERROR nodes. An attacker can use Bash brace expansion (e.g., {/bin/bash,-c,id}) or Zsh anonymous functions (e.g., (){ /bin/bash -c id }) as command substitutions within allowlisted commands like echo. The underlying shell still executes the hidden command while Vibe's approval logic only sees the benign outer command. This bypass requires no authentication or user interaction beyond issuing a crafted command. The recommended fix is to require explicit user approval whenever ERROR nodes appear in the parse tree, rather than trusting incomplete parse results.

Affected products

  • Mistral Vibe v1.3.4 and later

Timeline

  • 2026-09-11: disclosed

References

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