Distribution-over-TLS LAN allowlist silently bypassed due to sockname/peername confusion in inet_tls_dist

Weakness Type (CWE)

CWE-1025 — CWE-1025 Comparison Using Wrong Factors

CAPEC

CVSS 4.0 Score

7.5

HIGH

CVSS:4.0/AV:A/AC:H/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Vulnerability description

Reliance on IP Address for Authentication vulnerability in Erlang/OTP ssl (inet_tls_dist module) allows unauthenticated bypass of the distribution-over-TLS LAN allowlist.

The inet_tls_dist:check_ip/1 function, which enforces a LAN allowlist for Erlang distribution over TLS, calls inet:sockname/1 instead of inet:peername/1 to obtain the peer's IP address. Because inet:sockname/1 returns the local socket address, both the local IP and the supposed peer IP resolve to the same value, causing the subnet mask comparison to always succeed regardless of the actual remote address. Any holder of a CA-signed TLS certificate can therefore bypass the LAN restriction and gain full Erlang distribution access to the node, including rpc:call/4 and code:load_binary/3.

This vulnerability is associated with program file lib/ssl/src/inet_tls_dist.erl.

This issue affects OTP from OTP 26.0 before 29.0.2, 28.5.0.2 and 27.3.4.13 corresponding to ssl from 11.0 before 11.7.2, 11.6.0.2 and 11.2.12.9.

Affected

`pkg:otp/ssl`

Module	Source File	Routine
`inet_tls_dist`	`src/inet_tls_dist.erl`	`inet_tls_dist:check_ip/1`

Status	Type	Version	Changes / Fixed in
affected	otp ^ⓘ	`11.0`	unaffected at `11.7.2` unaffected at `11.6.0.2` unaffected at `11.2.12.9`

`pkg:github/erlang/otp`

Module	Source File	Routine
`inet_tls_dist`	`lib/ssl/src/inet_tls_dist.erl`	`inet_tls_dist:check_ip/1`

Status	Type	Version	Changes / Fixed in
affected	otp ^ⓘ	`26.0`	unaffected at `29.0.2` unaffected at `28.5.0.2` unaffected at `27.3.4.13`
affected	git ^ⓘ	`7a08c55078`	< `0209a6df65`

Configurations

The Erlang distribution must be configured to use TLS (inet_tls_dist) with the check_ip option enabled. The default Erlang distribution configuration does not use TLS and is not affected.

Workarounds

Implement a custom verify_fun SSL option that correctly checks the peer IP address using inet:peername/1 on the socket.

References

https://github.com/erlang/otp/security/advisories/GHSA-gp7x-mfv6-52cv vendor-advisory related
https://osv.dev/vulnerability/EEF-CVE-2026-48860 related
https://github.com/erlang/otp/commit/0209a6df65d605552b378273027b3968b35f26b4 patch

Credits

Finder: Lukas Backström
Remediation developer: Ingela Anderton Andin
Remediation reviewer: Raimo Niskanen
Remediation reviewer: Jakub Witczak

CVE record as JSON: GET /cves/CVE-2026-48860.json
OSV record as JSON: GET /osv/EEF-CVE-2026-48860.json