CVE-2026-114049 vllm-project CVE debrief

Who should care

Defenders responsible for vLLM deployments should assess exposure and apply patches or updates to prevent potential impact on client outputs. This includes operators, platform administrators, vulnerability management teams, and security teams who need to verify if their vLLM version is affected and take appropriate actions.

Why it matters

CVE-2026-114049 is a medium-severity vulnerability in vLLM before version 0.31.0 that allows remote attackers to constrain client outputs via stale allowed_token_ids rows. Defenders should assess exposure and apply patches or updates to prevent potential impact.

• Defenders need to verify if their vLLM version is affected and apply patches or updates to prevent potential client output constraints.
• Remote attackers can exploit this vulnerability to constrain client outputs, potentially impacting the functionality of affected systems.
• The vulnerability requires verification of affected versions and application of patches or updates to prevent exploitation.

Technical summary

The vulnerability is caused by a cross-request mask leak in InputBatch.condense() in vLLM before version 0.31.0. This allows remote attackers to constrain other clients' outputs by leaving stale allowed_token_ids rows. Attackers can submit concurrent constrained generate requests, including via unauthenticated /invocations, so recycled batch slots apply their token allowlist to victims' unrestricted requests.

Defensive priority

Medium priority for defenders to assess exposure and apply patches, as the vulnerability allows for potential impact on client outputs.

Recommended defensive actions

• Assess exposure by checking if the vLLM version is before 0.31.0
• Apply patches or updates to vLLM version 0.31.0 or later
• Monitor client outputs for potential constraints
• 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 vulnerability is described in the CVE Program record and the NVD vulnerability detail page. The source item provides additional information on the vulnerability, including affected versions and references to vendor advisories.

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.