Erlang OTP >=17.0/29.0.3 Megaco Flex Scanner megaco_flex_scanner_drv.flex.src mfs_load_property_groups parm name buffer overflow

Summaryinfo

A vulnerability was found in Erlang OTP >=17.0/29.0.3 and classified as critical. The impacted element is the function mfs_load_property_groups of the file lib/megaco/src/flex/megaco_flex_scanner_drv.flex.src of the component Megaco Flex Scanner. The manipulation of the argument parm name results in buffer overflow. This vulnerability was named CVE-2026-59250. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability was found in Erlang OTP >=17.0/29.0.3. It has been classified as critical. Affected is the function mfs_load_property_groups of the file lib/megaco/src/flex/megaco_flex_scanner_drv.flex.src of the component Megaco Flex Scanner. The manipulation of the argument parm name with an unknown input leads to a buffer overflow vulnerability. CWE is classifying the issue as CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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 until OTP 29.0.4, 28.5.0.4, and 27.3.4.15 corresponding to megaco from 3.17.1 until 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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-59250 since 07/04/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit.

Upgrading to version 29.0.4, 28.5.0.4 or 27.3.4.15 eliminates this vulnerability.

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Productinfo

Vendor

• Erlang

Name

• OTP

Version

• 29.0.3
• >=17.0

Website

• Product: https://github.com/erlang/otp/

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