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CVE-2026-73299

CRITICAL 10

Published 2026-08-12 · Last modified 2026-08-12

Prompty is a markdown file format (.prompty) for LLM prompts. Prior to 0.1.5 and 2.0.0-beta.5, the TypeScript Nunjucks renderer evaluated untrusted .prompty template bodies with unrestricted JavaScript member access. An attacker-controlled template could traverse constructor and prototype properties to execute JavaScript in the host Node.js process. This issue is fixed in versions 0.1.5 and 2.0.0-beta.5.

ELEVATED IMPACT

Severe if exploited (CVSS 10), but no known exploitation and low modeled probability. Patch on a normal cadence.

Exploitation likelihood

1.2%chance of exploitation in 30 days · 66th percentile

○ In CISA KEV ○ Public exploit / PoC

Impact if exploited

10CVSS 3.1 · CRITICAL

  • ConfidentialityHigh
  • IntegrityHigh
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

Test against your own equipment

curl -s https://vulnpedia.com/cve/CVE-2026-73299/poc.jsonMachine-readable PoC index for this CVE (for automation).

Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-73299/poc.json

Affected

Vendors Microsoft

Products Prompty

Weakness (CWE)

  • CWE-94: : Improper Control of Generation of Code ('Code Injection')
  • CWE-1336: : Improper Neutralization of Special Elements Used in a Template Engine

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

All CVSS metrics

  • CRITICAL 10 v3.1 · CNA Primary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
  • CRITICAL 10 v3.1 · NVD Secondary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

References

Technical & other

Sources: NVD · CVE.org · EPSS