FKIE_CVE-2021-33193
Vulnerability from fkie_nvd - Published: 2021-08-16 08:15 - Updated: 2026-06-17 03:54
Severity
Summary
A crafted method sent through HTTP/2 will bypass validation and be forwarded by mod_proxy, which can lead to request splitting or cache poisoning. This issue affects Apache HTTP Server 2.4.17 to 2.4.48.
References
Impacted products
| Vendor | Product | Version | |
|---|---|---|---|
| debian | debian_linux | 10.0 | |
| apache | http_server | * | |
| fedoraproject | fedora | 34 | |
| fedoraproject | fedora | 35 | |
| tenable | tenable.sc | * | |
| oracle | secure_backup | * | |
| oracle | zfs_storage_appliance_kit | 8.8 |
{
"affected": [
{
"affectedData": [
{
"product": "Apache HTTP Server",
"vendor": "Apache Software Foundation",
"versions": [
{
"status": "affected",
"version": "Apache HTTP Server 2.4 2.4.17 to 2.4.48"
}
]
}
],
"source": "security@apache.org"
}
],
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"vulnerable": true
}
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],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "A crafted method sent through HTTP/2 will bypass validation and be forwarded by mod_proxy, which can lead to request splitting or cache poisoning. This issue affects Apache HTTP Server 2.4.17 to 2.4.48."
},
{
"lang": "es",
"value": "Un m\u00e9todo dise\u00f1ado enviado mediante HTTP/2 omitir\u00e1 la comprobaci\u00f3n y ser\u00e1 reenviado por mod_proxy, lo que puede conllevar a la divisi\u00f3n de peticiones o el envenenamiento de la cach\u00e9. Este problema afecta a Apache HTTP Server versiones 2.4.17 a 2.4.48."
}
],
"id": "CVE-2021-33193",
"lastModified": "2026-06-17T03:54:19.957",
"metrics": {
"cvssMetricV2": [
{
"acInsufInfo": false,
"baseSeverity": "MEDIUM",
"cvssData": {
"accessComplexity": "LOW",
"accessVector": "NETWORK",
"authentication": "NONE",
"availabilityImpact": "NONE",
"baseScore": 5.0,
"confidentialityImpact": "NONE",
"integrityImpact": "PARTIAL",
"vectorString": "AV:N/AC:L/Au:N/C:N/I:P/A:N",
"version": "2.0"
},
"exploitabilityScore": 10.0,
"impactScore": 2.9,
"obtainAllPrivilege": false,
"obtainOtherPrivilege": false,
"obtainUserPrivilege": false,
"source": "nvd@nist.gov",
"type": "Primary",
"userInteractionRequired": false
}
],
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "NONE",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 3.6,
"source": "nvd@nist.gov",
"type": "Primary"
}
]
},
"published": "2021-08-16T08:15:11.480",
"references": [
{
"source": "security@apache.org",
"tags": [
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],
"url": "https://github.com/apache/httpd/commit/ecebcc035ccd8d0e2984fe41420d9e944f456b3c.patch"
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},
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},
{
"source": "security@apache.org",
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"url": "https://portswigger.net/research/http2"
},
{
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"url": "https://security.gentoo.org/glsa/202208-20"
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"tags": [
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],
"url": "https://security.netapp.com/advisory/ntap-20210917-0004/"
},
{
"source": "security@apache.org",
"tags": [
"Third Party Advisory"
],
"url": "https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ"
},
{
"source": "security@apache.org",
"tags": [
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"url": "https://www.oracle.com/security-alerts/cpuapr2022.html"
},
{
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"url": "https://www.oracle.com/security-alerts/cpujan2022.html"
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{
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"url": "https://www.tenable.com/security/tns-2021-17"
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"sourceIdentifier": "security@apache.org",
"vulnStatus": "Analyzed",
"weaknesses": [
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"description": [
{
"lang": "en",
"value": "NVD-CWE-Other"
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],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
}
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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.
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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.
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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.
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