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PatchSiren cyber security CVE debrief

CVE-2026-34939 MervinPraison CVE debrief

A vulnerability in PraisonAI's MCPToolIndex.search_tools() function allows for catastrophic backtracking, leading to a service outage. The issue was patched in version 4.5.90. This vulnerability has a CVSS score of 6.5 and a severity of MEDIUM. The CVE record was published on 2026-04-03T23:17:06.330Z and was last modified on 2026-07-24T22:10:00.140Z.

Vendor
MervinPraison
Product
PraisonAI
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-03
Original CVE updated
2026-07-24
Advisory published
2026-04-03
Advisory updated
2026-07-24

Who should care

Users of PraisonAI versions prior to 4.5.90 should update to the latest version to prevent potential service outages. This vulnerability has a CVSS score of 6.5 and a severity of MEDIUM, indicating a moderate level of risk. Operators, platform administrators, vulnerability management teams, and security teams should review their deployments and take necessary actions.

Technical summary

The MCPToolIndex.search_tools() function in PraisonAI compiles a caller-supplied string directly as a Python regular expression without validation, sanitization, or timeout. A crafted regex can cause catastrophic backtracking in the re engine, blocking the Python thread for hundreds of seconds and causing a complete service outage. This issue has been patched in version 4.5.90. Users of PraisonAI versions prior to 4.5.90 should update to the latest version to prevent potential service outages.

Defensive priority

High

Recommended defensive actions

  • Update PraisonAI to version 4.5.90 or later
  • Implement input validation and sanitization for regular expressions
  • Monitor for potential service outages
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-04-03T23:17:06.330Z and was last modified on 2026-07-24T22:10:00.140Z. The NVD entry is currently Analyzed. The PraisonAI MCPToolIndex.search_tools() function vulnerability allows for catastrophic backtracking, leading to a service outage. Users should verify their deployments and review official advisories for affected scope and vendor guidance.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-34939 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-34939

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-34939 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-34939

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.