GHSA-j828-28rj-hfhp is a medium-severity (CVSS 4.3) CWE-1333 vulnerability in vllm. A fix is available for vllm — see the affected versions and patch details below.
vLLM vulnerable to Regular Expression Denial of Service
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-j828-28rj-hfhp.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-j828-28rj-hfhp plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
vllmReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
A recent review identified several regular expressions in the vllm codebase that are susceptible to Regular Expression Denial of Service (ReDoS) attacks. These patterns, if fed with crafted or malicious input, may cause severe performance degradation due to catastrophic backtracking.
1. vllm/lora/utils.py Line 173
https://github.com/vllm-project/vllm/blob/2858830c39da0ae153bc1328dbba7680f5fbebe1/vllm/lora/utils.py#L173 Risk Description:
- The regex
r"\((.*?)\)\$?$"matches content inside parentheses. If input such as((((a|)+)+)+)is passed in, it can cause catastrophic backtracking, leading to a ReDoS vulnerability. - Using
.*?(non-greedy match) inside group parentheses can be highly sensitive to input length and nesting complexity.
Remediation Suggestions:
- Limit the input string length.
- Use a non-recursive matching approach, or write a regex with stricter content constraints.
- Consider using possessive quantifiers or atomic groups (not supported in Python yet), or split and process before regex matching.
2. vllm/entrypoints/openai/tool_parsers/phi4mini_tool_parser.py Line 52
Risk Description:
- The regex
r'functools\[(.*?)\]'uses.*?to match content inside brackets, together withre.DOTALL. If the input contains a large number of nested or crafted brackets, it can cause backtracking and ReDoS.
Remediation Suggestions:
- Limit the length of
model_output. - Use a stricter, non-greedy pattern (avoid matching across extraneous nesting).
- Prefer
re.finditer()and enforce a length constraint on each match.
3. vllm/entrypoints/openai/serving_chat.py Line 351
Risk Description:
- The regex
r'.*"parameters":\s*(.*)'can trigger backtracking ifcurrent_textis very long and contains repeated structures. - Especially when processing strings from unknown sources,
.*matching any content is high risk.
Remediation Suggestions:
- Use a more specific pattern (e.g., via JSON parsing).
- Impose limits on
current_textlength. - Avoid using
.*to capture large blocks of text; prefer structured parsing when possible.
4. benchmarks/benchmark_serving_structured_output.py Line 650
Risk Description:
- The regex
r'\{.*\}'is used to extract JSON inside curly braces. If theactualstring is very long with unbalanced braces, it can cause backtracking, leading to a ReDoS vulnerability. - Although this is used for benchmark correctness checking, it should still handle abnormal inputs carefully.
Remediation Suggestions:
- Limit the length of
actual. - Prefer stepwise search for
{and}or use a robust JSON extraction tool. - Recommend first locating the range with simple string search, then applying regex.
Fix
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | vllm | ≥ 0.6.3&&< 0.9.0 | 0.9.0pip install --upgrade 'vllm==0.9.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vllm, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update vllm to 0.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-j828-28rj-hfhp is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-j828-28rj-hfhp can be triaged on real exposure rather than presence alone.
Tailored to GHSA-j828-28rj-hfhp. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-j828-28rj-hfhp in your dependencies?
O3 Security finds GHSA-j828-28rj-hfhp across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.