CVE-2026-49755 (GCVE-0-2026-49755)
Vulnerability from cvelistv5 – Published: 2026-06-08 15:20 – Updated: 2026-06-08 17:14
VLAI
EPSS
VEX
Title
Decompression bomb DoS in Req via auto-decoded archive and compressed response bodies
Summary
Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in wojtekmach Req allows attacker-controlled HTTP servers to exhaust memory in a Req client via decompression-bomb response bodies.
Req's default response pipeline includes Req.Steps.decode_body/1 and Req.Steps.decompress_body/1 in lib/req/steps.ex. decode_body/1 dispatches on the server-supplied content-type (or URL extension) and calls :zip.extract(body, [:memory]) for application/zip, :erl_tar.extract({:binary, body}, [:memory]) for application/x-tar, and :erl_tar.extract({:binary, body}, [:memory, :compressed]) for application/gzip / .tgz. Each returns the full decompressed archive contents as a [{name, bytes}] list in memory, with no per-entry or total size cap. decompress_body/1 walks the content-encoding header and chains :zlib/:brotli/:ezstd decoders, so a response advertising content-encoding: gzip, gzip, gzip inflates through multiple layers without bound.
Both steps are enabled by default, no caller opt-in is required, and the attacker controls the content-type and content-encoding headers on their own server (or on any host reached via Req's automatic redirect following). A sub-megabyte response can expand to multiple gigabytes on the victim, crashing the BEAM process.
This issue affects req: from 0.1.0 before 0.6.1.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-08 16:49 UTC
CWE
- CWE-409 - Improper Handling of Highly Compressed Data (Data Amplification)
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/wojtekmach/req/security/adviso… | vendor-advisoryrelated |
| https://cna.erlef.org/cves/CVE-2026-49755.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-49755 | related |
| https://github.com/wojtekmach/req/commit/84977e5b… | patch |
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| wojtekmach | req |
Affected:
0.1.0 , < 0.6.1
(semver)
cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:* |
||
| wojtekmach | req |
Affected:
e37753741cbdc725e6aba3d977b380163bfc0ecb , < 84977e5b1a83f26e749d55ad06e3625464af4e8d
(git)
cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:* |
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"url": "https://github.com/wojtekmach/req/commit/84977e5b1a83f26e749d55ad06e3625464af4e8d"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"tags": [
"Vendor Advisory",
"Exploit",
"Patch"
],
"url": "https://github.com/wojtekmach/req/security/advisories/GHSA-655f-mp8p-96gv"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"tags": [
"Third Party Advisory",
"Patch",
"Mitigation"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-49755"
},
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"tags": [
"Vendor Advisory",
"Exploit",
"Patch"
],
"url": "https://github.com/wojtekmach/req/security/advisories/GHSA-655f-mp8p-96gv"
}
],
"sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"vulnStatus": "Analyzed",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-409"
}
],
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
}
]
}
},
"redhat_vex": {
"current_release_date": "2026-06-09T20:59:25+00:00",
"cve": "CVE-2026-49755",
"id": "CVE-2026-49755",
"initial_release_date": "2026-01-01T00:00:00+00:00",
"product_status:known_not_affected": "1",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "Decompression bomb DoS in Req via auto-decoded archive and compressed response bodies",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49755.json",
"version": "3"
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-49755",
"options": [
{
"Exploitation": "poc"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-06-08T16:49:57.977214Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-06-08T16:49:41.908Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"exploit"
],
"url": "https://github.com/wojtekmach/req/security/advisories/GHSA-655f-mp8p-96gv"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://repo.hex.pm",
"cpes": [
"cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.Req.Steps\u0027"
],
"packageName": "req",
"packageURL": "pkg:hex/req",
"product": "req",
"programFiles": [
"lib/req/steps.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.Req.Steps\u0027:decode_body/1"
},
{
"name": "\u0027Elixir.Req.Steps\u0027:decompress_body/1"
}
],
"repo": "https://github.com/wojtekmach/req",
"vendor": "wojtekmach",
"versions": [
{
"lessThan": "0.6.1",
"status": "affected",
"version": "0.1.0",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.Req.Steps\u0027"
],
"packageName": "wojtekmach/req",
"packageURL": "pkg:github/wojtekmach/req",
"product": "req",
"programFiles": [
"lib/req/steps.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.Req.Steps\u0027:decode_body/1"
},
{
"name": "\u0027Elixir.Req.Steps\u0027:decompress_body/1"
}
],
"repo": "https://github.com/wojtekmach/req.git",
"vendor": "wojtekmach",
"versions": [
{
"lessThan": "84977e5b1a83f26e749d55ad06e3625464af4e8d",
"status": "affected",
"version": "e37753741cbdc725e6aba3d977b380163bfc0ecb",
"versionType": "git"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:*",
"versionEndExcluding": "0.6.1",
"versionStartIncluding": "0.1.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
],
"operator": "AND"
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Peter Ullrich"
},
{
"lang": "en",
"type": "remediation developer",
"value": "Wojtek Mach"
},
{
"lang": "en",
"type": "analyst",
"value": "Jonatan M\u00e4nnchen / EEF"
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in wojtekmach Req allows attacker-controlled HTTP servers to exhaust memory in a Req client via decompression-bomb response bodies.\u003cp\u003eReq\u0027s default response pipeline includes \u003ctt\u003e\u0027Elixir.Req.Steps\u0027:decode_body/1\u003c/tt\u003e and \u003ctt\u003e\u0027Elixir.Req.Steps\u0027:decompress_body/1\u003c/tt\u003e in \u003ctt\u003elib/req/steps.ex\u003c/tt\u003e. \u003ctt\u003edecode_body/1\u003c/tt\u003e dispatches on the server-supplied \u003ctt\u003econtent-type\u003c/tt\u003e (or URL extension) and calls \u003ctt\u003e:zip.extract(body, [:memory])\u003c/tt\u003e for \u003ctt\u003eapplication/zip\u003c/tt\u003e, \u003ctt\u003e:erl_tar.extract({:binary, body}, [:memory])\u003c/tt\u003e for \u003ctt\u003eapplication/x-tar\u003c/tt\u003e, and \u003ctt\u003e:erl_tar.extract({:binary, body}, [:memory, :compressed])\u003c/tt\u003e for \u003ctt\u003eapplication/gzip\u003c/tt\u003e / \u003ctt\u003e.tgz\u003c/tt\u003e. Each returns the full decompressed archive contents as a \u003ctt\u003e[{name, bytes}]\u003c/tt\u003e list in memory, with no per-entry or total size cap. \u003ctt\u003edecompress_body/1\u003c/tt\u003e walks the \u003ctt\u003econtent-encoding\u003c/tt\u003e header and chains \u003ctt\u003e:zlib\u003c/tt\u003e/\u003ctt\u003e:brotli\u003c/tt\u003e/\u003ctt\u003e:ezstd\u003c/tt\u003e decoders, so a response advertising \u003ctt\u003econtent-encoding: gzip, gzip, gzip\u003c/tt\u003e inflates through multiple layers without bound.\u003c/p\u003e\u003cp\u003eBoth steps are enabled by default, no caller opt-in is required, and the attacker controls the \u003ctt\u003econtent-type\u003c/tt\u003e and \u003ctt\u003econtent-encoding\u003c/tt\u003e headers on their own server (or on any host reached via Req\u0027s automatic redirect following). A sub-megabyte response can expand to multiple gigabytes on the victim, crashing the BEAM process.\u003c/p\u003e\u003cp\u003eThis issue affects req: from 0.1.0 before 0.6.1.\u003c/p\u003e"
}
],
"value": "Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in wojtekmach Req allows attacker-controlled HTTP servers to exhaust memory in a Req client via decompression-bomb response bodies.\n\nReq\u0027s default response pipeline includes Req.Steps.decode_body/1 and Req.Steps.decompress_body/1 in lib/req/steps.ex. decode_body/1 dispatches on the server-supplied content-type (or URL extension) and calls :zip.extract(body, [:memory]) for application/zip, :erl_tar.extract({:binary, body}, [:memory]) for application/x-tar, and :erl_tar.extract({:binary, body}, [:memory, :compressed]) for application/gzip / .tgz. Each returns the full decompressed archive contents as a [{name, bytes}] list in memory, with no per-entry or total size cap. decompress_body/1 walks the content-encoding header and chains :zlib/:brotli/:ezstd decoders, so a response advertising content-encoding: gzip, gzip, gzip inflates through multiple layers without bound.\n\nBoth steps are enabled by default, no caller opt-in is required, and the attacker controls the content-type and content-encoding headers on their own server (or on any host reached via Req\u0027s automatic redirect following). A sub-megabyte response can expand to multiple gigabytes on the victim, crashing the BEAM process.\n\nThis issue affects req: from 0.1.0 before 0.6.1."
}
],
"impacts": [
{
"capecId": "CAPEC-197",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-197 Exponential Data Expansion"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 8.2,
"baseSeverity": "HIGH",
"privilegesRequired": "NONE",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "HIGH",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-409",
"description": "CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-06-08T17:14:08.858Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
},
"references": [
{
"tags": [
"vendor-advisory",
"related"
],
"url": "https://github.com/wojtekmach/req/security/advisories/GHSA-655f-mp8p-96gv"
},
{
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-49755.html"
},
{
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-49755"
},
{
"tags": [
"patch"
],
"url": "https://github.com/wojtekmach/req/commit/84977e5b1a83f26e749d55ad06e3625464af4e8d"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Decompression bomb DoS in Req via auto-decoded archive and compressed response bodies",
"workarounds": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eDisable Req\u0027s automatic body decoding on requests that fetch attacker-influenced URLs by passing \u003ctt\u003edecode_body: false\u003c/tt\u003e to \u003ctt\u003e\u0027Elixir.Req\u0027:new/1\u003c/tt\u003e / \u003ctt\u003e\u0027Elixir.Req\u0027:get!/1\u003c/tt\u003e. To also skip the \u003ctt\u003econtent-encoding\u003c/tt\u003e decompression pipeline, pass \u003ctt\u003eraw: true\u003c/tt\u003e. Both options leave the response body as the raw on-the-wire bytes, so the caller can size-check before any decompression.\u003c/p\u003e"
}
],
"value": "Disable Req\u0027s automatic body decoding on requests that fetch attacker-influenced URLs by passing decode_body: false to Req.new/1 / Req.get!/1. To also skip the content-encoding decompression pipeline, pass raw: true. Both options leave the response body as the raw on-the-wire bytes, so the caller can size-check before any decompression."
}
],
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-49755",
"datePublished": "2026-06-08T15:20:57.415Z",
"dateReserved": "2026-06-01T13:45:22.448Z",
"dateUpdated": "2026-06-08T17:14:08.858Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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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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