NVD / CVE Program· CNA GitHub_M

CVE-2026-55574: vLLM: ReDoS via structured_outputs.regex compiled without timeout in xgrammar and outlines backends

Noroxi assessment

Priority: Monitor (action score 34/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.58% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: vllm-project vllm 0.24.0.

Low priority for now. Upgrade to vllm-project vllm 0.24.0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

vLLM is a high-throughput and memory-efficient inference and serving engine for LLMs. Prior to 0.24.0, the structured_outputs.regex API parameter passes a user-supplied regular expression string directly to the grammar compiler backends with no compilation timeout; in the xgrammar backend the string reaches the regex compiler with no guard, and in the outlines backend the validation step blocks structural issues such as lookarounds and backreferences but performs no complexity analysis, so a pattern with nested quantifiers passes all checks and causes exponential state-space expansion, allowing a single request containing an adversarial regex to hang an inference worker indefinitely and deny service. This issue is fixed in version 0.24.0.

HighCVSS 8.7 · v4.0—No exploit Fix available

Published: Jul 6, 2026
Updated: Oct 25, 2026
EPSS: 0.5% · 47th percentile
CWE: CWE-1333

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 34 / 40 · 8.7 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.5%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · GitHub_M: 8.7; NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
vllm	vllm	cpe:2.3:a:vllm:vllm

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

vllm vllmbefore 0.24.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

vllm-project vllm
- < 0.24.0affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
PyPI	vllm	before 0.24.0	0.24.0

Same product

vllm: all records

Other highest-scoring records for the same primary product.

CVE-2026-22778vLLM leaks a heap address when PIL throws an error
60This week
CVE-2025-32444vLLM Vulnerable to Remote Code Execution via Mooncake Integration
40Plan
CVE-2024-11041Remote Code Execution in vllm-project/vllm
40Plan

Published before and after this one in the same product

← EarlierCVE-2026-54234Jul 6, 2026 · vLLM: Remote DoS in vLLM via Invalid Recovered Token Reinjection
30Monitor
← EarlierCVE-2026-55514Jul 6, 2026 · vLLM denial of service via prompt embeds on M-RoPE models
28Monitor
Later →CVE-2026-73555Aug 13, 2026 · vLLM: Unauthenticated Internal Path and Username Disclosure via Validation Error Messages
21Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
vllm-project vllm	0.24.0 · description	Vendor (CNA)
PyPI:vllm	0.24.0	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2025-46560433 days apartvLLM phi4mm: Quadratic Time Complexity in Input Token Processing leads to denial of service
30Monitor
CVE-2025-48887402 days apartvLLM has a Regular Expression Denial of Service (ReDoS, Exponential Complexity) Vulnerability in `pythonic_tool_parser.py`
26Monitor
CVE-2025-7137916 days apartvllm - Regular Expression Denial of Service in Multiple Components
21Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: X

Weakness class (CWE)

CWE-1333 · Inefficient Regular Expression Complexity

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

Regular Expression Exponential BlowupCAPEC-492

ATT&CK techniques

—

Change log

Fix✗ → ✓Sep 28, 2026, 10:45 PM UTC

For records you follow, these changes also arrive as notifications. →

References

github.com/vllm-project/vllm/commit/2b3006076c5e9bc4cda9e03e3641388de3c5c286

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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