PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-54236 vllm-project CVE debrief

CVE-2026-54236 is a vulnerability in vLLM, an inference and serving engine for large language models (LLMs). The incomplete fix for CVE-2026-22778 allows an unauthenticated attacker to send malformed image bytes through the Anthropic Messages API image content parts, leaking the heap memory address verbatim in the error.message field of the response body. This issue was fixed in version 0.23.1rc0. The vulnerability has a CVSS score of 5.3 and a severity of MEDIUM. The CVE was published on 2026-06-22T23:16:31.290Z and modified on 2026-06-24T16:53:59.157Z.

Vendor
vllm-project
Product
vllm
CVSS
MEDIUM 5.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-22
Original CVE updated
2026-06-24
Advisory published
2026-06-22
Advisory updated
2026-06-24

Who should care

Defenders of systems using vLLM should be aware of this vulnerability and take steps to mitigate it. Specifically, those using versions prior to 0.23.1rc0 should update to the latest version. Additionally, defenders should monitor their systems for potential exploitation attempts.

Technical summary

The vulnerability in vLLM arises from an incomplete fix for CVE-2026-22778. The sanitize_message helper, which strips object-repr memory addresses from error messages, is not called in several response paths, including the Anthropic API router, Server-Sent Events streaming converter, and realtime speech-to-text WebSocket. This allows an unauthenticated attacker to leak heap memory addresses by sending malformed image bytes through the Anthropic Messages API.

Defensive priority

Defenders should prioritize updating to version 0.23.1rc0 or later. Additionally, defenders should monitor their systems for potential exploitation attempts and implement compensating controls to detect and prevent similar attacks.

Recommended defensive actions

  • Update to version 0.23.1rc0 or later
  • Monitor systems for potential exploitation attempts
  • Implement compensating controls to detect and prevent similar attacks
  • Review and update incident response plans
  • Conduct vulnerability scanning and penetration testing

Evidence notes

The CVE-2026-54236 vulnerability was introduced due to an incomplete fix for CVE-2026-22778. The issue was discovered and reported by an unknown party. The CVE was published on 2026-06-22T23:16:31.290Z and modified on 2026-06-24T16:53:59.157Z. The vulnerability has a CVSS score of 5.3 and a severity of MEDIUM.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-54236 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-54236

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

  • CVE-2026-54236 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-54236

    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.