FKIE_CVE-2026-4867
Vulnerability from fkie_nvd - Published: 2026-03-26 17:16 - Updated: 2026-06-17 10:57
Severity
Summary
Impact:
A bad regular expression is generated any time you have three or more parameters within a single segment, separated by something that is not a period (.). For example, /:a-:b-:c or /:a-:b-:c-:d. The backtrack protection added in path-to-regexp@0.1.12 only prevents ambiguity for two parameters. With three or more, the generated lookahead does not block single separator characters, so capture groups overlap and cause catastrophic backtracking.
Patches:
Upgrade to path-to-regexp@0.1.13
Custom regex patterns in route definitions (e.g., /:a-:b([^-/]+)-:c([^-/]+)) are not affected because they override the default capture group.
Workarounds:
All versions can be patched by providing a custom regular expression for parameters after the first in a single segment. As long as the custom regular expression does not match the text before the parameter, you will be safe. For example, change /:a-:b-:c to /:a-:b([^-/]+)-:c([^-/]+).
If paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length.
References
| URL | Tags | ||
|---|---|---|---|
| ce714d77-add3-4f53-aff5-83d477b104bb | https://blakeembrey.com/posts/2024-09-web-redos | Technical Description | |
| ce714d77-add3-4f53-aff5-83d477b104bb | https://cna.openjsf.org/security-advisories.html | Third Party Advisory | |
| ce714d77-add3-4f53-aff5-83d477b104bb | https://github.com/advisories/GHSA-9wv6-86v2-598j | Not Applicable |
Impacted products
| Vendor | Product | Version | |
|---|---|---|---|
| pillarjs | path-to-regexp | * |
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"packageURL": "pkg:npm/path-to-regexp",
"product": "path-to-regexp",
"vendor": "path-to-regexp",
"versions": [
{
"lessThan": "0.1.13",
"status": "affected",
"version": "0",
"versionType": "semver"
}
]
}
],
"source": "ce714d77-add3-4f53-aff5-83d477b104bb"
}
],
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:pillarjs:path-to-regexp:*:*:*:*:*:node.js:*:*",
"matchCriteriaId": "AD9DFD27-4A53-4409-9DAC-8E326EBB3303",
"versionEndExcluding": "0.1.13",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "Impact:\n\nA bad regular expression is generated any time you have three or more parameters within a single segment, separated by something that is not a period (.). For example, /:a-:b-:c or /:a-:b-:c-:d. The backtrack protection added in path-to-regexp@0.1.12 only prevents ambiguity for two parameters. With three or more, the generated lookahead does not block single separator characters, so capture groups overlap and cause catastrophic backtracking.\n\nPatches:\n\nUpgrade to path-to-regexp@0.1.13\n\nCustom regex patterns in route definitions (e.g., /:a-:b([^-/]+)-:c([^-/]+)) are not affected because they override the default capture group.\n\nWorkarounds:\n\nAll versions can be patched by providing a custom regular expression for parameters after the first in a single segment. As long as the custom regular expression does not match the text before the parameter, you will be safe. For example, change /:a-:b-:c to /:a-:b([^-/]+)-:c([^-/]+).\n\nIf paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length."
},
{
"lang": "es",
"value": "Impacto:\n\nSe genera una expresi\u00f3n regular incorrecta cada vez que se tienen tres o m\u00e1s par\u00e1metros dentro de un \u00fanico segmento, separados por algo que no sea un punto (.). Por ejemplo, /:a-:b-:c o /:a-:b-:c-:d. La protecci\u00f3n contra retroceso a\u00f1adida en path-to-regexp@0.1.12 solo previene la ambig\u00fcedad para dos par\u00e1metros. Con tres o m\u00e1s, el \u0027lookahead\u0027 generado no bloquea los caracteres separadores individuales, por lo que los grupos de captura se superponen y causan un retroceso catastr\u00f3fico.\n\nParches:\n\nActualizar a path-to-regexp@0.1.13\n\nLos patrones de expresiones regulares personalizados en las definiciones de ruta (por ejemplo, /:a-:b([^-/]+)-:c([^-/]+)) no se ven afectados porque anulan el grupo de captura predeterminado.\n\nSoluciones provisionales:\n\nTodas las versiones pueden ser parcheadas proporcionando una expresi\u00f3n regular personalizada para los par\u00e1metros despu\u00e9s del primero en un \u00fanico segmento. Siempre y cuando la expresi\u00f3n regular personalizada no coincida con el texto anterior al par\u00e1metro, estar\u00e1 seguro. Por ejemplo, cambie /:a-:b-:c a /:a-:b([^-/]+)-:c([^-/]+).\n\nSi las rutas no pueden ser reescritas y las versiones no pueden ser actualizadas, otra alternativa es limitar la longitud de la URL."
}
],
"id": "CVE-2026-4867",
"lastModified": "2026-06-17T10:57:21.827",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 3.6,
"source": "ce714d77-add3-4f53-aff5-83d477b104bb",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-4867",
"options": [
{
"exploitation": "none"
},
{
"automatable": "yes"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-03-26T16:52:08.810671Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-03-26T17:16:42.983",
"references": [
{
"source": "ce714d77-add3-4f53-aff5-83d477b104bb",
"tags": [
"Technical Description"
],
"url": "https://blakeembrey.com/posts/2024-09-web-redos"
},
{
"source": "ce714d77-add3-4f53-aff5-83d477b104bb",
"tags": [
"Third Party Advisory"
],
"url": "https://cna.openjsf.org/security-advisories.html"
},
{
"source": "ce714d77-add3-4f53-aff5-83d477b104bb",
"tags": [
"Not Applicable"
],
"url": "https://github.com/advisories/GHSA-9wv6-86v2-598j"
}
],
"sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb",
"vulnStatus": "Analyzed",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-1333"
}
],
"source": "ce714d77-add3-4f53-aff5-83d477b104bb",
"type": "Secondary"
}
]
}
Loading…
Loading…
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
Loading timeline…
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.