CVE-2026-107290 pydantic CVE debrief

Who should care

Defenders responsible for Pydantic AI installations, specifically those using versions 1.77.0 to 1.107.6 and 2.44.0, should assess exposure and prioritize patching to prevent potential DoS attacks.

Why it matters

CVE-2026-107290 is a medium-severity vulnerability in Pydantic AI's `web_fetch` tool that can lead to denial-of-service (DoS) attacks. Defenders should prioritize patching vulnerable versions to prevent potential attacks.

• Potential denial-of-service (DoS) attacks against Pydantic AI installations
• Stalling of other agent runs and requests due to blocked event loop
• Verification of inventory and patching of vulnerable versions required

Technical summary

Pydantic AI's `web_fetch` tool is vulnerable to quadratic title extraction, which can cause the event loop to block, stalling other agent runs and requests. This issue affects versions 1.77.0 to 1.107.6 and 2.44.0, and is fixed in versions 1.107.6 and 2.44.0. The vulnerability has a medium severity and can lead to denial-of-service (DoS) attacks. Defenders should prioritize patching vulnerable versions to prevent potential attacks. The CVE record and source item provide details on the vulnerability, including affected versions and fixed versions.

Defensive priority

Defenders should prioritize patching vulnerable versions of Pydantic AI, specifically versions 1.77.0 to 1.107.6 and 2.44.0, to prevent potential DoS attacks.

Recommended defensive actions

• Patch vulnerable versions of Pydantic AI to prevent potential DoS attacks
• Verify inventory of Pydantic AI installations to identify potential exposure
• Monitor for suspicious activity related to `web_fetch` tool usage
• 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 and source item provide details on the vulnerability, including affected versions (1.77.0 to 1.107.6 and 2.44.0) and fixed versions (1.107.6 and 2.44.0). However, there is limited information on potential exploitation or victim impact. Defenders should verify inventory and patch vulnerable versions to prevent potential DoS attacks. The vulnerability has a medium severity and can lead to denial-of-service (DoS) attacks. There is no evidence of exploitation in the wild, but defenders should monitor for suspicious activity

Sources and 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.