CVE-2026-119434 (GCVE-0-2026-119434)
Vulnerability from cvelistv5 – Published: 2026-11-05 20:15 – Updated: 2026-11-05 20:45
VLAI
EPSS
VEX
Title
Decompression bomb in ezstd:decompress_using_ddict/2 allows BEAM memory exhaustion via unbounded output buffer
Summary
Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in silviucpp ezstd allows an attacker who supplies a zstd frame to ezstd:decompress_using_ddict/2 to exhaust memory and terminate the Erlang VM via a small frame that declares a very large content size.
zstd_nif_decompress_using_ddict in c_src/ezstd_nif.cc reads the frame's declared content size with ZSTD_getFrameContentSize and passes it directly to enif_make_new_binary, without the 1 GiB MAX_BUFFER_SIZE check that ezstd:decompress/1 applies before allocating. A valid 65,550-byte frame of RLE blocks declaring 2 GiB is rejected by ezstd:decompress/1 but is fully allocated and decompressed by the dictionary path. The allocation happens inside a NIF, so when it exceeds the memory available to the VM the operating system kills the whole node rather than the calling process.
This issue affects ezstd: from 1.0.5 before 1.2.5.
Severity
6.2 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-11-05 20:45 UTC
CWE
- CWE-409 - Improper Handling of Highly Compressed Data (Data Amplification)
Assigner
References
5 references
| URL | Tags |
|---|---|
| https://github.com/silviucpp/ezstd/releases/tag/v1.2.5 | release-notesrelated |
| https://cna.erlef.org/cves/CVE-2026-119434.html | relatedthird-party-advisory |
| https://osv.dev/vulnerability/EEF-CVE-2026-119434 | related |
| https://github.com/silviucpp/ezstd/commit/6730128… | related |
| https://github.com/silviucpp/ezstd/commit/e34f4a4… | patch |
Impacted products
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"title": "Decompression bomb in ezstd:decompress_using_ddict/2 allows BEAM memory exhaustion via unbounded output buffer",
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"value": "\u003cp\u003e\u003cstrong\u003e1. Declared size is attacker controlled.\u003c/strong\u003e A zstd frame header carries an optional Frame Content Size field. \u003ccode\u003ezstd_nif_decompress_using_ddict\u003c/code\u003e in \u003ccode\u003ec_src/ezstd_nif.cc\u003c/code\u003e reads it with \u003ccode\u003eZSTD_getFrameContentSize\u003c/code\u003e and rejects only the two sentinel values \u003ccode\u003eZSTD_CONTENTSIZE_UNKNOWN\u003c/code\u003e and \u003ccode\u003eZSTD_CONTENTSIZE_ERROR\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2. Unbounded allocation.\u003c/strong\u003e The size is passed directly to \u003ccode\u003eenif_make_new_binary\u003c/code\u003e, so a frame declaring 2 GiB makes the NIF request a 2 GiB binary. The sibling \u003ccode\u003ezstd_nif_decompress\u003c/code\u003e rejects any declared size above \u003ccode\u003eMAX_BUFFER_SIZE\u003c/code\u003e (1 GiB) before allocating; the dictionary path omitted that check from the commit that introduced it.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3. Amplification.\u003c/strong\u003e A frame built from RLE blocks, each encoding 128 KiB of a repeated byte in four bytes, declares and genuinely decompresses to 2 GiB from 65,550 bytes of input, a ratio of about 32,760:1. \u003ccode\u003eZSTD_decompress_usingDDict\u003c/code\u003e then fills the buffer. Because this happens inside a NIF, exceeding the memory available to the VM results in the operating system killing the whole BEAM process rather than an Erlang-level exception.\u003c/p\u003e"
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"value": "**1. Declared size is attacker controlled.** A zstd frame header carries an optional Frame Content Size field. `zstd_nif_decompress_using_ddict` in `c_src/ezstd_nif.cc` reads it with `ZSTD_getFrameContentSize` and rejects only the two sentinel values `ZSTD_CONTENTSIZE_UNKNOWN` and `ZSTD_CONTENTSIZE_ERROR`.\n\n**2. Unbounded allocation.** The size is passed directly to `enif_make_new_binary`, so a frame declaring 2 GiB makes the NIF request a 2 GiB binary. The sibling `zstd_nif_decompress` rejects any declared size above `MAX_BUFFER_SIZE` (1 GiB) before allocating; the dictionary path omitted that check from the commit that introduced it.\n\n**3. Amplification.** A frame built from RLE blocks, each encoding 128 KiB of a repeated byte in four bytes, declares and genuinely decompresses to 2 GiB from 65,550 bytes of input, a ratio of about 32,760:1. `ZSTD_decompress_usingDDict` then fills the buffer. Because this happens inside a NIF, exceeding the memory available to the VM results in the operating system killing the whole BEAM process rather than an Erlang-level exception."
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"value": "1. Declared size is attacker controlled. A zstd frame header carries an optional Frame Content Size field. zstd_nif_decompress_using_ddict in c_src/ezstd_nif.cc reads it with ZSTD_getFrameContentSize and rejects only the two sentinel values ZSTD_CONTENTSIZE_UNKNOWN and ZSTD_CONTENTSIZE_ERROR.\n\n2. Unbounded allocation. The size is passed directly to enif_make_new_binary, so a frame declaring 2 GiB makes the NIF request a 2 GiB binary. The sibling zstd_nif_decompress rejects any declared size above MAX_BUFFER_SIZE (1 GiB) before allocating; the dictionary path omitted that check from the commit that introduced it.\n\n3. Amplification. A frame built from RLE blocks, each encoding 128 KiB of a repeated byte in four bytes, declares and genuinely decompresses to 2 GiB from 65,550 bytes of input, a ratio of about 32,760:1. ZSTD_decompress_usingDDict then fills the buffer. Because this happens inside a NIF, exceeding the memory available to the VM results in the operating system killing the whole BEAM process rather than an Erlang-level exception."
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"value": "1. Build ezstd 1.2.4 and start a VM under an external memory limit, for example a container limited to 256 MiB.\n2. Create any decompression dictionary with `ezstd:create_ddict/1`; its content does not matter because the frame carries no dictionary ID.\n3. Construct a zstd frame: the magic number, a frame header descriptor selecting an 8-byte content size, a window descriptor, a little-endian content size of 2 GiB, then 16,383 RLE blocks of 128 KiB each (block header `0x02 0x00 0x10` followed by one payload byte) and a final RLE block with the last-block bit set. The frame is 65,550 bytes.\n4. Call `ezstd:decompress/1` on the frame: it returns `{error, \u003c\u003c\"frame too large or invalid\"\u003e\u003e}`.\n5. Call `ezstd:decompress_using_ddict/2` on the same frame with the dictionary: the VM is killed by the operating system (exit status 137).\n6. Repeat on 1.2.5: the call returns `{error, \u003c\u003c\"frame too large or invalid\"\u003e\u003e}` and the VM continues."
}
],
"value": "* Build ezstd 1.2.4 and start a VM under an external memory limit, for example a container limited to 256 MiB.\n* Create any decompression dictionary with ezstd:create_ddict/1; its content does not matter because the frame carries no dictionary ID.\n* Construct a zstd frame: the magic number, a frame header descriptor selecting an 8-byte content size, a window descriptor, a little-endian content size of 2 GiB, then 16,383 RLE blocks of 128 KiB each (block header 0x02 0x00 0x10 followed by one payload byte) and a final RLE block with the last-block bit set. The frame is 65,550 bytes.\n* Call ezstd:decompress/1 on the frame: it returns {error, \u003c\u003c\"frame too large or invalid\"\u003e\u003e}.\n* Call ezstd:decompress_using_ddict/2 on the same frame with the dictionary: the VM is killed by the operating system (exit status 137).\n* Repeat on 1.2.5: the call returns {error, \u003c\u003c\"frame too large or invalid\"\u003e\u003e} and the VM continues."
}
],
"x_technicalAnalysis": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003e\u003cstrong\u003e1. Declared size is attacker controlled.\u003c/strong\u003e A zstd frame header carries an optional Frame Content Size field. \u003ccode\u003ezstd_nif_decompress_using_ddict\u003c/code\u003e in \u003ccode\u003ec_src/ezstd_nif.cc\u003c/code\u003e reads it with \u003ccode\u003eZSTD_getFrameContentSize\u003c/code\u003e and rejects only the two sentinel values \u003ccode\u003eZSTD_CONTENTSIZE_UNKNOWN\u003c/code\u003e and \u003ccode\u003eZSTD_CONTENTSIZE_ERROR\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2. Unbounded allocation.\u003c/strong\u003e The size is passed directly to \u003ccode\u003eenif_make_new_binary\u003c/code\u003e, so a frame declaring 2 GiB makes the NIF request a 2 GiB binary. The sibling \u003ccode\u003ezstd_nif_decompress\u003c/code\u003e rejects any declared size above \u003ccode\u003eMAX_BUFFER_SIZE\u003c/code\u003e (1 GiB) before allocating; the dictionary path omitted that check from the commit that introduced it.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3. Amplification.\u003c/strong\u003e A frame built from RLE blocks, each encoding 128 KiB of a repeated byte in four bytes, declares and genuinely decompresses to 2 GiB from 65,550 bytes of input, a ratio of about 32,760:1. \u003ccode\u003eZSTD_decompress_usingDDict\u003c/code\u003e then fills the buffer. Because this happens inside a NIF, exceeding the memory available to the VM results in the operating system killing the whole BEAM process rather than an Erlang-level exception.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "**1. Declared size is attacker controlled.** A zstd frame header carries an optional Frame Content Size field. `zstd_nif_decompress_using_ddict` in `c_src/ezstd_nif.cc` reads it with `ZSTD_getFrameContentSize` and rejects only the two sentinel values `ZSTD_CONTENTSIZE_UNKNOWN` and `ZSTD_CONTENTSIZE_ERROR`.\n\n**2. Unbounded allocation.** The size is passed directly to `enif_make_new_binary`, so a frame declaring 2 GiB makes the NIF request a 2 GiB binary. The sibling `zstd_nif_decompress` rejects any declared size above `MAX_BUFFER_SIZE` (1 GiB) before allocating; the dictionary path omitted that check from the commit that introduced it.\n\n**3. Amplification.** A frame built from RLE blocks, each encoding 128 KiB of a repeated byte in four bytes, declares and genuinely decompresses to 2 GiB from 65,550 bytes of input, a ratio of about 32,760:1. `ZSTD_decompress_usingDDict` then fills the buffer. Because this happens inside a NIF, exceeding the memory available to the VM results in the operating system killing the whole BEAM process rather than an Erlang-level exception."
}
],
"value": "1. Declared size is attacker controlled. A zstd frame header carries an optional Frame Content Size field. zstd_nif_decompress_using_ddict in c_src/ezstd_nif.cc reads it with ZSTD_getFrameContentSize and rejects only the two sentinel values ZSTD_CONTENTSIZE_UNKNOWN and ZSTD_CONTENTSIZE_ERROR.\n\n2. Unbounded allocation. The size is passed directly to enif_make_new_binary, so a frame declaring 2 GiB makes the NIF request a 2 GiB binary. The sibling zstd_nif_decompress rejects any declared size above MAX_BUFFER_SIZE (1 GiB) before allocating; the dictionary path omitted that check from the commit that introduced it.\n\n3. Amplification. A frame built from RLE blocks, each encoding 128 KiB of a repeated byte in four bytes, declares and genuinely decompresses to 2 GiB from 65,550 bytes of input, a ratio of about 32,760:1. ZSTD_decompress_usingDDict then fills the buffer. Because this happens inside a NIF, exceeding the memory available to the VM results in the operating system killing the whole BEAM process rather than an Erlang-level exception."
}
]
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-119434",
"datePublished": "2026-11-05T20:15:56.311Z",
"dateReserved": "2026-10-30T10:30:01.015Z",
"dateUpdated": "2026-11-05T20:45:33.490Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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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.
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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.