Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
The vLLM package, versions before 0.26.0, is vulnerable to a denial-of-service attack through the structured_outputs regex option when the lm-format-enforcer backend is selected. The regex is compiled with no timeout or validation, so a single request with a catastrophic pattern can stall the structured-output engine worker. An unauthenticated attacker who can send requests to a server configured with this backend can cause this stall. Upgrade to vLLM 0.26.0 or later, which fixes the issue.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 5.3 | Medium | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0052, the 44th percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:10 UTC First seen by agentprime
- 31 Oct 2026, 14:10 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-48jh-3gj7-fg8v
- OSV: GHSA-48jh-3gj7-fg8v
- github.com/vllm-project/vllm/security/advisories/GHSA-48jh-3gj7-fg8v
- nvd.nist.gov/vuln/detail/CVE-2026-73556
- github.com/vllm-project/vllm/pull/47595
- github.com/vllm-project/vllm/commit/c9a788eedc412acceaa5112e0d44624b49841577
- github.com/vllm-project/vllm
- github.com/vllm-project/vllm/releases/tag/v0.26.0