CVE-2026-59250 (GCVE-0-2026-59250)
Vulnerability from cvelistv5 – Published: 2026-07-27 15:25 – Updated: 2026-07-28 09:55
VLAI
EPSS
VEX
Title
Megaco flex scanner buffer overflow via oversized property parm name
Summary
Classic buffer overflow in the Erlang/OTP megaco flex scanner C driver allows a remote unauthenticated attacker to corrupt the driver's memory (and potentially achieve remote code execution or a denial-of-service crash) by sending a single text-encoded H.248/Megaco message containing an oversized property parm name.
When tokenizing a Local/Remote descriptor, mfs_load_property_groups extracts the attacker-controlled property name (bounded only by the message length) and, when no value follows, formats it into a fixed 512-byte error_msg field of the MfsErlDrvData struct using an unchecked sprintf call. Names longer than roughly 452 bytes overflow into the immediately following struct fields (text_buf, text_ptr, term_spec, term_spec_size, term_spec_index), overwriting live pointers and counters with attacker-chosen bytes. Subsequent scanner code writes and frees through the corrupted pointers, producing arbitrary write and arbitrary free primitives inside the BEAM VM process, which can be leveraged for remote code execution. On builds compiled with _FORTIFY_SOURCE the overflow is detected at runtime and terminates the process with SIGABRT, resulting in denial of service.
The overflow occurs in the flex scanner before any grammar or Megaco-level authentication processing, so exploitation requires only network reachability to the megaco transport port on a node configured with {scanner, flex}.
This vulnerability is associated with program files lib/megaco/src/flex/megaco_flex_scanner_drv.flex.src and program routines mfs_load_property_groups.
This issue affects OTP from OTP 17.0 before OTP 29.0.4, OTP 28.5.0.4 and OTP 27.3.4.15, corresponding to megaco from 3.17.1 before 4.9.1, 4.8.3.1 and 4.7.2.2. Versions prior to OTP 17.0 are also affected but are not listed because the OTP version scheme is only defined from OTP 17.0 onwards.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
Assigner
References
5 references
| URL | Tags |
|---|---|
| https://github.com/erlang/otp/security/advisories… | vendor-advisoryrelated |
| https://cna.erlef.org/cves/CVE-2026-59250.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-59250 | related |
| https://www.erlang.org/doc/system/versions.html#o… | x_version-scheme |
| https://github.com/erlang/otp/commit/8704c8f550a1… | patch |
Impacted products
2 products
Credits
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"containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-59250\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-07-27T18:33:04.735708Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-07-27T18:33:10.223Z\"}}], \"cna\": {\"title\": \"Megaco flex scanner buffer overflow via oversized property parm name\", \"source\": {\"discovery\": \"INTERNAL\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"Jonatan M\\u00e4nnchen / EEF\"}, {\"lang\": \"en\", \"type\": \"remediation developer\", \"value\": \"Jakub Witczak\"}, {\"lang\": \"en\", \"type\": \"remediation reviewer\", \"value\": \"Micael Karlberg\"}], \"impacts\": [{\"capecId\": \"CAPEC-100\", \"descriptions\": [{\"lang\": \"en\", \"value\": \"CAPEC-100 Overflow Buffers\"}]}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"version\": \"4.0\", \"baseScore\": 8.3, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"PRESENT\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"LOW\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"HIGH\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"NONE\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"cpes\": [\"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\"], \"repo\": \"https://github.com/erlang/otp\", \"vendor\": \"Erlang\", \"modules\": [\"megaco_flex_scanner\", \"megaco_flex_scanner_drv\"], \"product\": \"OTP\", \"versions\": [{\"status\": \"affected\", \"changes\": [{\"at\": \"4.9.1\", \"status\": \"unaffected\"}, {\"at\": \"4.8.3.1\", \"status\": \"unaffected\"}, {\"at\": \"4.7.2.2\", \"status\": \"unaffected\"}], \"version\": \"3.17.1\", \"lessThan\": \"*\", \"versionType\": \"otp\"}], \"packageURL\": \"pkg:otp/megaco?repository_url=https:%2F%2Fgithub.com%2Ferlang%2Fotp\u0026vcs_url=git%20https:%2F%2Fgithub.com%2Ferlang%2Fotp.git\", \"packageName\": \"megaco\", \"programFiles\": [\"src/flex/megaco_flex_scanner_drv.flex.src\"], \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"mfs_load_property_groups\"}, {\"name\": \"megaco_flex_scanner:scan/2\"}]}, {\"cpes\": [\"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\"], \"repo\": \"https://github.com/erlang/otp\", \"vendor\": \"Erlang\", \"modules\": [\"megaco_flex_scanner\", \"megaco_flex_scanner_drv\"], \"product\": \"OTP\", \"versions\": [{\"status\": \"affected\", \"changes\": [{\"at\": \"29.0.4\", \"status\": \"unaffected\"}, {\"at\": \"28.5.0.4\", \"status\": \"unaffected\"}, {\"at\": \"27.3.4.15\", \"status\": \"unaffected\"}], \"version\": \"R13B03\", \"lessThan\": \"*\", \"versionType\": \"otp\"}, {\"status\": \"affected\", \"version\": \"84adefa331c4159d432d22840663c38f155cd4c1\", \"lessThan\": \"8704c8f550a11ed5f825e3c011ecb03565b79c4f\", \"versionType\": \"git\"}], \"packageURL\": \"pkg:github/erlang/otp\", \"packageName\": \"erlang/otp\", \"programFiles\": [\"lib/megaco/src/flex/megaco_flex_scanner_drv.flex.src\"], \"collectionURL\": \"https://github.com\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"mfs_load_property_groups\"}, {\"name\": \"megaco_flex_scanner:scan/2\"}]}], \"references\": [{\"url\": \"https://github.com/erlang/otp/security/advisories/GHSA-7xgh-gmgf-q2g7\", \"tags\": [\"vendor-advisory\", \"related\"]}, {\"url\": \"https://cna.erlef.org/cves/CVE-2026-59250.html\", \"tags\": [\"related\"]}, {\"url\": \"https://osv.dev/vulnerability/EEF-CVE-2026-59250\", \"tags\": [\"related\"]}, {\"url\": \"https://www.erlang.org/doc/system/versions.html#order-of-versions\", \"tags\": [\"x_version-scheme\"]}, {\"url\": \"https://github.com/erlang/otp/commit/8704c8f550a11ed5f825e3c011ecb03565b79c4f\", \"tags\": [\"patch\"]}], \"workarounds\": [{\"lang\": \"en\", \"value\": \"Switch the megaco text codec to the default Erlang-based scanner by removing {scanner, flex} from the encoder configuration. The Erlang scanner is not affected by this C-level memory corruption, at the cost of reduced parsing throughput.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eSwitch the megaco text codec to the default Erlang-based scanner by removing \u003ctt\u003e{scanner, flex}\u003c/tt\u003e from the encoder configuration. The Erlang scanner is not affected by this C-level memory corruption, at the cost of reduced parsing throughput.\u003c/p\u003e\", \"base64\": false}]}], \"x_generator\": {\"engine\": \"cvelib 1.8.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"Classic buffer overflow in the Erlang/OTP megaco flex scanner C driver allows a remote unauthenticated attacker to corrupt the driver\u0027s memory (and potentially achieve remote code execution or a denial-of-service crash) by sending a single text-encoded H.248/Megaco message containing an oversized property parm name.\\n\\nWhen tokenizing a Local/Remote descriptor, mfs_load_property_groups extracts the attacker-controlled property name (bounded only by the message length) and, when no value follows, formats it into a fixed 512-byte error_msg field of the MfsErlDrvData struct using an unchecked sprintf call. Names longer than roughly 452 bytes overflow into the immediately following struct fields (text_buf, text_ptr, term_spec, term_spec_size, term_spec_index), overwriting live pointers and counters with attacker-chosen bytes. Subsequent scanner code writes and frees through the corrupted pointers, producing arbitrary write and arbitrary free primitives inside the BEAM VM process, which can be leveraged for remote code execution. On builds compiled with _FORTIFY_SOURCE the overflow is detected at runtime and terminates the process with SIGABRT, resulting in denial of service.\\n\\nThe overflow occurs in the flex scanner before any grammar or Megaco-level authentication processing, so exploitation requires only network reachability to the megaco transport port on a node configured with {scanner, flex}.\\n\\nThis vulnerability is associated with program files lib/megaco/src/flex/megaco_flex_scanner_drv.flex.src and program routines mfs_load_property_groups.\\n\\nThis issue affects OTP from OTP 17.0 before OTP\\u00a029.0.4, OTP\\u00a028.5.0.4 and OTP\\u00a027.3.4.15, corresponding to megaco from 3.17.1 before 4.9.1, 4.8.3.1 and 4.7.2.2. Versions prior to OTP 17.0 are also affected but are not listed because the OTP version scheme is only defined from OTP 17.0 onwards.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eClassic buffer overflow in the Erlang/OTP megaco flex scanner C driver allows a remote unauthenticated attacker to corrupt the driver\u0027s memory (and potentially achieve remote code execution or a denial-of-service crash) by sending a single text-encoded H.248/Megaco message containing an oversized property parm name.\u003c/p\u003e\u003cp\u003eWhen tokenizing a Local/Remote descriptor, \u003ctt\u003emfs_load_property_groups\u003c/tt\u003e extracts the attacker-controlled property name (bounded only by the message length) and, when no value follows, formats it into a fixed 512-byte \u003ctt\u003eerror_msg\u003c/tt\u003e field of the \u003ctt\u003eMfsErlDrvData\u003c/tt\u003e struct using an unchecked \u003ctt\u003esprintf\u003c/tt\u003e call. Names longer than roughly 452 bytes overflow into the immediately following struct fields (\u003ctt\u003etext_buf\u003c/tt\u003e, \u003ctt\u003etext_ptr\u003c/tt\u003e, \u003ctt\u003eterm_spec\u003c/tt\u003e, \u003ctt\u003eterm_spec_size\u003c/tt\u003e, \u003ctt\u003eterm_spec_index\u003c/tt\u003e), overwriting live pointers and counters with attacker-chosen bytes. Subsequent scanner code writes and frees through the corrupted pointers, producing arbitrary write and arbitrary free primitives inside the BEAM VM process, which can be leveraged for remote code execution. On builds compiled with \u003ctt\u003e_FORTIFY_SOURCE\u003c/tt\u003e the overflow is detected at runtime and terminates the process with \u003ctt\u003eSIGABRT\u003c/tt\u003e, resulting in denial of service.\u003c/p\u003e\u003cp\u003eThe overflow occurs in the flex scanner before any grammar or Megaco-level authentication processing, so exploitation requires only network reachability to the megaco transport port on a node configured with \u003ctt\u003e{scanner, flex}\u003c/tt\u003e.\u003c/p\u003e\u003cp\u003eThis vulnerability is associated with program files \u003ctt\u003elib/megaco/src/flex/megaco_flex_scanner_drv.flex.src\u003c/tt\u003e and program routines \u003ctt\u003emfs_load_property_groups\u003c/tt\u003e.\u003c/p\u003e\u003cp\u003eThis issue affects OTP from OTP 17.0 before OTP\u0026nbsp;29.0.4, OTP\u0026nbsp;28.5.0.4 and OTP\u0026nbsp;27.3.4.15, corresponding to megaco from 3.17.1 before 4.9.1, 4.8.3.1 and 4.7.2.2. Versions prior to OTP 17.0 are also affected but are not listed because the OTP version scheme is only defined from OTP 17.0 onwards.\u003c/p\u003e\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-120\", \"description\": \"CWE-120 Buffer Copy without Checking Size of Input (\u0027Classic Buffer Overflow\u0027)\"}, {\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-787\", \"description\": \"CWE-787 Out-of-bounds Write\"}]}], \"configurations\": [{\"lang\": \"en\", \"value\": \"The megaco text codec must be configured to use the flex scanner via the encoder option {scanner, flex} (the documented high-performance configuration). Deployments using the default Erlang-based scanner are not affected.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eThe megaco text codec must be configured to use the flex scanner via the encoder option \u003ctt\u003e{scanner, flex}\u003c/tt\u003e (the documented high-performance configuration). Deployments using the default Erlang-based scanner are not affected.\u003c/p\u003e\", \"base64\": false}]}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"27.3.4.15\"}, {\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"28.5.0.4\", \"versionStartIncluding\": \"28.0\"}, {\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"29.0.4\", \"versionStartIncluding\": \"29.0\"}], \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-07-28T09:55:21.416Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-59250\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-07-28T09:55:21.416Z\", \"dateReserved\": \"2026-07-04T04:24:03.653Z\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"datePublished\": \"2026-07-27T15:25:03.106Z\", \"assignerShortName\": \"EEF\"}",
"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.
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