CVE-2026-56340
CVE-2026-56340 is a high-severity vulnerability in Vllm with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.
Key facts
- Severity: High (CVSS 3.x base score 8.8)
- CVSS v4: 8.7
- EPSS exploit prediction: 0% (27th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-38129
- Weakness: CWE-20
- Affected product: Vllm
- Published:
- Last modified:
Description
vLLM versions >= 0.10.2 and < 0.13.0 are missing sparse tensor validation in multimodal embeddings processing. Because PyTorch disables sparse tensor invariant checks by default, an attacker can submit crafted embedding requests with malformed (negative or out-of-bounds) tensor indices, when the prompt-embeds feature is enabled, to trigger crashes or resource exhaustion (denial of service), with potential for out-of-bounds/write-what-where memory corruption. This continues CVE-2025-62164, whose prior fix only disabled the feature by default rather than addressing the root cause.
Frequently asked questions
- What is CVE-2026-56340?
- vLLM versions >= 0.10.2 and < 0.13.0 are missing sparse tensor validation in multimodal embeddings processing. Because PyTorch disables sparse tensor invariant checks by default, an attacker can submit crafted embedding requests with malformed (negative or out-of-bounds) tensor indices, when the prompt-embeds feature is enabled, to trigger crashes or resource exhaustion (denial of service), with potential for out-of-bounds/write-what-where memory corruption. This continues CVE-2025-62164, whose prior fix only disabled the feature by default rather than addressing the root cause.
- How severe is CVE-2026-56340?
- CVE-2026-56340 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
- Is CVE-2026-56340 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-56340?
- CVE-2026-56340 affects Vllm. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2026-56340?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- Does CVE-2026-56340 have an EU (EUVD) identifier?
- Yes. CVE-2026-56340 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38129.
- When was CVE-2026-56340 published?
- CVE-2026-56340 was published on 2026-06-20 and last updated on 2026-06-30.
References
- https://github.com/vllm-project/vllm/security/advisories/GHSA-mcmc-2m55-j8jj
- https://www.vulncheck.com/advisories/vllm-denial-of-service-via-unvalidated-multimodal-embeddings
- https://access.redhat.com/security/cve/CVE-2026-56340
- https://bugzilla.redhat.com/show_bug.cgi?id=2491060
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-56340.json
Affected products (1)
- cpe:2.3:a:vllm:vllm:*:*:*:*:*:*:*:*
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