CVE-2026-75538: A Signed Length Overflow in Erlang/OTP's inet TCP Driver Overflows the Receive Buffer Into BEAM VM Memory From an Unauthenticated Peer
Summary
An attacker that connects to an open Erlang TCP port that uses the inet driver with {packet,4} mode can use a signed overflow in an incorrect packet length calculation to overflow the receive buffer into the VM allocator area and beyond up to about 2 GB.
This would easily trash the allocated block's allocator metadata footer, and the next block, if any, and most likely cause the BEAM VM to crash. Utilizing this with precision enough to achieve Remote Code Execution would be extremely unfeasible.
This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, OTP 28.5.0.6, and OTP 29.0.6, corresponding to erts from 6.0 before 15.2.7.13, 16.4.0.6, and 17.0.6. Whether OTP before OTP 17.0, corresponding to erts before 6.0, is affected is unknown.
Other sources
A Signed Length Overflow in Erlang/OTP's inet TCP Driver Overflows the Receive Buffer Into BEAM VM Memory From an Unauthenticated Peer
— Microsoft
An attacker that connects to an open Erlang TCP port that uses the inet driver with {packet,4} mode can use a signed overflow in an incorrect packet length calculation to overflow the receive buffer into the VM allocator area and beyond up to about 2 GB.
— Launchpad
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 26.2.5.21-6 - Upgrade
Upgrade
debian/erlangto a version that resolves this vulnerability.Fixed in 1:27.3.4.1+dfsg-1+deb13u4 - Upgrade
Upgrade
debian/erlangto a version that resolves this vulnerability.Fixed in 1:29.0.6+dfsg-1 - Upgrade
Upgrade
debian/erlangto a version that resolves this vulnerability.Fixed in 1:27.3.4.1+dfsg-1+deb13u4Fixed in 1:29.1.2+dfsg-1 - Upgrade
Upgrade
Erlang/OTPto a version that resolves this vulnerability.Fixed in 27.3.4.17 - Upgrade
Upgrade
Erlang/OTPto a version that resolves this vulnerability.Fixed in 28.5.0.6 - Upgrade
Upgrade
Erlang/OTPto a version that resolves this vulnerability.Fixed in 29.0.6
Event History
Frequently Asked Questions
Which Erlang services are exposed to this issue?
Services with an open TCP port using the inet driver in {packet,4} mode are exposed. An unauthenticated remote peer only needs to connect to such a port.
What is the likely impact of exploitation?
The overflow can corrupt allocator metadata and adjacent memory, most likely crashing the BEAM VM. The available information describes remote code execution as extremely unfeasible.
Which releases contain fixes?
Update affected OTP 17.x releases to 27.3.4.17 or later, OTP 28.x releases to 28.5.0.6 or later, or OTP 29.x releases to 29.0.6 or later. OTP versions before 17.0 are of unknown status.
What can be done before an update is available?
Avoid exposing TCP endpoints configured with the inet driver and {packet,4} mode to untrusted peers. Restricting access to those ports limits the unauthenticated network attack path described for this issue.