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CVE-2026-59250· NVD / CVE Program· CNA EEF

Megaco flex scanner buffer overflow via oversized property parm name

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 27.3.4.15, from OTP 28.0 before OTP 28.5.0.4, and from OTP 29.0 before OTP 29.0.4, corresponding to megaco from 3.17.1 before 4.7.2.2, from 4.8 before 4.8.3.1, and from 4.9 before 4.9.1. Whether OTP before OTP 17.0, corresponding to megaco before 3.17.1, is affected is unknown.

HighCVSS 8.3 · v4.0—No exploit Fix available
Published
Jul 27, 2026
Updated
Sep 8, 2026
EPSS
0.8% · 55th percentile
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Report tools

JSON

Action score

33

Monitor

Low priority for now.

CVSS
33 / 40 · 8.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.8%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · EEF
8.3
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Noroxi analysis

No Noroxi analysis for this record yet

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Affected systems

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (EEF). Independent of NVD's CPE analysis and usually ahead of it.

  • Erlang OTP

    • before 17.0unknown · otp
    • 17.0 and later · before 27.3.4.15affected · otp
    • 28.0 and later · before 28.5.0.4affected · otp
    • 29.0 and later · before 29.0.4affected · otp
    • before 3.17.1unknown · otp
    • 3.17.1 and later · before 4.7.2.2affected · otp
    • 4.8 and later · before 4.8.3.1affected · otp
    • 4.9 and later · before 4.9.1affected · otp
    • 84adefa331c4159d432d22840663c38f155cd4c1 and later · before 8704c8f550a11ed5f825e3c011ecb03565b79c4faffected · git

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12erlangall versions—
Debian:13erlangbefore 1:27.3.4.1+dfsg-1+deb13u31:27.3.4.1+dfsg-1+deb13u3
Debian:14erlangbefore 1:29.0.4+dfsg-11:29.0.4+dfsg-1
openSUSE:Tumbleweederlang27before 27.1.3-3.127.1.3-3.1
Red Hat:hummingbird:1erlang27before 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-asn1before 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-common_testbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-compilerbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-cryptobefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-debuggerbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-dialyzerbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-diameterbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-edocbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-eldapbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-erl_interfacebefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-ertsbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-etbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-eunitbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-examplesbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-ftpbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-gdb-toolsbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-inetsbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-jinterfacebefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
Red Hat:hummingbird:1erlang27-kernelbefore 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1

+20

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Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Erlang OTP27.3.4.15Vendor (CNA)
Erlang OTP28.5.0.4Vendor (CNA)
Erlang OTP29.0.4Vendor (CNA)
Erlang OTP4.7.2.2Vendor (CNA)
Erlang OTP4.8.3.1Vendor (CNA)
Erlang OTP4.9.1Vendor (CNA)
Erlang OTP8704c8f550a11ed5f825e3c011ecb03565b79c4fVendor (CNA)
azl3 erlang 26.2.5.21-4 on Azure Linux 3.026.2.5.21-5 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:erlang1:27.3.4.1+dfsg-1+deb13u3 · Debian:13Package registry (OSV)
opensuse:erlang2727.1.3-3.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:erlang270:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-asn10:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-common_test0:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-compiler0:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-crypto0:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-debugger0:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-dialyzer0:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-diameter0:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-edoc0:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-eldap0:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-erl_interface0:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:erlang27-erts0:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
suse:erlang23.3.4.19-150300.3.39.1 · SUSE:Linux Enterprise Module for Server Applications 15 SP7Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-120 · Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

CVSS vector

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Root cause

When data is copied, the source length is not compared with the size of the destination buffer. Excess data overwrites adjacent memory.

The bug in code

The whole CWE-120 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

c
char buf[256];memcpy(buf, pkt->data, pkt->len);

Fixed

c
char buf[256];if (pkt->len > sizeof(buf)) {  return -EINVAL;}memcpy(buf, pkt->data, pkt->len);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records