CVE-2026-34939
Praisonai ≤ 4.5.90
Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HSummary
CVE-2026-34939 is a medium-severity Inefficient Regular Expression Complexity (CWE-1333) vulnerability in Praison Praisonai. Its CVSS base score is 6.5 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked at the 33th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-34939 affects PraisonAI, a multi-agent teams system, specifically in the MCPToolIndex.search_tools() function prior to version 4.5.90. The vulnerability arises from compiling a caller-supplied string directly as a Python regular expression without validation, sanitization, or timeout mechanisms. This enables catastrophic backtracking in the Python re engine, which can block the Python thread for hundreds of seconds and result in a complete service outage. The issue is classified under CWE-1333 with a CVSS v3.1 base score of 6.5 (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
An attacker with low privileges (PR:L) can exploit this over the network (AV:N) with low complexity and no user interaction required. By supplying a crafted regex string to the search_tools() function, the attacker triggers excessive backtracking, consuming CPU resources and halting the affected Python thread, leading to denial-of-service that impacts service availability across the system.
The vulnerability has been addressed in PraisonAI version 4.5.90. Security practitioners should upgrade to this version or later. Additional details are available in the GitHub Security Advisory at https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-8w9j-hc3g-3g7f.
As a multi-agent teams system, PraisonAI has relevance to AI/ML workflows, where tool indexing functions like this may be invoked in agent coordination scenarios. No public reports of real-world exploitation are available as of the CVE publication on 2026-04-03.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-18921
Vulnerability Data
PraisonAI is a multi-agent teams system. Prior to version 4.5.90, MCPToolIndex.search_tools() compiles a caller-supplied string directly as a Python regular expression with no validation, sanitization, or timeout. A crafted regex causes catastrophic backtracking in the re engine, blocking the Python…
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thread for hundreds of seconds and causing a complete service outage. This issue has been patched in version 4.5.90.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation can discover inefficient regex patterns via performance or static analysis.
Development standards and tools can require safe regex construction and forbid known exponential patterns.
Denial-of-service protections limit resource exhaustion caused by expensive regex evaluation.
Input validation can constrain data that would otherwise trigger worst-case regex complexity.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can detect and reject regex patterns with exponential worst-case complexity.
Secure development lifecycle mandates review of algorithmic efficiency, directly addressing ReDoS-prone regex.
Application security requirements can specify input-validation rules that limit regex complexity.
Secure architecture principles encourage avoidance of computationally expensive constructs such as catastrophic backtracking.
Secure coding standards explicitly prohibit or limit the use of inefficient regular expressions.