CVE-2026-49755 (GCVE-0-2026-49755)

Vulnerability from cvelistv5 – Published: 2026-06-08 15:20 – Updated: 2026-06-08 17:14
VLAI
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
8.2 (High)
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
SSVC
Exploitation: poc Automatable: no Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-409 - Improper Handling of Highly Compressed Data (Data Amplification)
Assigner
EEF
References
Impacted products
Vendor Product Version
wojtekmach req Affected: 0.1.0 , < 0.6.1 (semver)
    cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:*
 Create a notification for this product.
wojtekmach req Affected: e37753741cbdc725e6aba3d977b380163bfc0ecb , < 84977e5b1a83f26e749d55ad06e3625464af4e8d (git)
    cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:*
 Create a notification for this product.
Credits
Peter Ullrich Wojtek Mach Jonatan Männchen / EEF
Show details on NVD website
To clipboard 

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    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-49755\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"poc\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-06-08T16:49:57.977214Z\"}}}], \"references\": [{\"url\": \"https://github.com/wojtekmach/req/security/advisories/GHSA-655f-mp8p-96gv\", \"tags\": [\"exploit\"]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-06-08T16:49:41.908Z\"}}], \"cna\": {\"title\": \"Decompression bomb DoS in Req via auto-decoded archive and compressed response bodies\", \"source\": {\"discovery\": \"EXTERNAL\"}, \"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\"}], \"impacts\": [{\"capecId\": \"CAPEC-197\", \"descriptions\": [{\"lang\": \"en\", \"value\": \"CAPEC-197 Exponential Data Expansion\"}]}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"version\": \"4.0\", \"baseScore\": 8.2, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"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\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"PRESENT\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"NONE\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"HIGH\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"NONE\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"cpes\": [\"cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:*\"], \"repo\": \"https://github.com/wojtekmach/req\", \"vendor\": \"wojtekmach\", \"modules\": [\"\u0027Elixir.Req.Steps\u0027\"], \"product\": \"req\", \"versions\": [{\"status\": \"affected\", \"version\": \"0.1.0\", \"lessThan\": \"0.6.1\", \"versionType\": \"semver\"}], \"packageURL\": \"pkg:hex/req\", \"packageName\": \"req\", \"programFiles\": [\"lib/req/steps.ex\"], \"collectionURL\": \"https://repo.hex.pm\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"\u0027Elixir.Req.Steps\u0027:decode_body/1\"}, {\"name\": \"\u0027Elixir.Req.Steps\u0027:decompress_body/1\"}]}, {\"cpes\": [\"cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:*\"], \"repo\": \"https://github.com/wojtekmach/req.git\", \"vendor\": \"wojtekmach\", \"modules\": [\"\u0027Elixir.Req.Steps\u0027\"], \"product\": \"req\", \"versions\": [{\"status\": \"affected\", \"version\": \"e37753741cbdc725e6aba3d977b380163bfc0ecb\", \"lessThan\": \"84977e5b1a83f26e749d55ad06e3625464af4e8d\", \"versionType\": \"git\"}], \"packageURL\": \"pkg:github/wojtekmach/req\", \"packageName\": \"wojtekmach/req\", \"programFiles\": [\"lib/req/steps.ex\"], \"collectionURL\": \"https://github.com\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"\u0027Elixir.Req.Steps\u0027:decode_body/1\"}, {\"name\": \"\u0027Elixir.Req.Steps\u0027:decompress_body/1\"}]}], \"references\": [{\"url\": \"https://github.com/wojtekmach/req/security/advisories/GHSA-655f-mp8p-96gv\", \"tags\": [\"vendor-advisory\", \"related\"]}, {\"url\": \"https://cna.erlef.org/cves/CVE-2026-49755.html\", \"tags\": [\"related\"]}, {\"url\": \"https://osv.dev/vulnerability/EEF-CVE-2026-49755\", \"tags\": [\"related\"]}, {\"url\": \"https://github.com/wojtekmach/req/commit/84977e5b1a83f26e749d55ad06e3625464af4e8d\", \"tags\": [\"patch\"]}], \"workarounds\": [{\"lang\": \"en\", \"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.\", \"supportingMedia\": [{\"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\", \"base64\": false}]}], \"x_generator\": {\"engine\": \"cvelib 1.8.0\"}, \"descriptions\": [{\"lang\": \"en\", \"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.\", \"supportingMedia\": [{\"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\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-409\", \"description\": \"CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)\"}]}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"0.6.1\", \"versionStartIncluding\": \"0.1.0\"}], \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-06-08T17:14:08.858Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-49755\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-06-08T17:14:08.858Z\", \"dateReserved\": \"2026-06-01T13:45:22.448Z\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"datePublished\": \"2026-06-08T15:20:57.415Z\", \"assignerShortName\": \"EEF\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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Taxonomy of the tags.





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.


Detection rules are retrieved from Rulezet.