Skip to content
Fencer Intel
medium 6.3

CVE-2026-123635 json

Refused calls drain the HTTP/2 connection flow-control window in elixir-grpc grpc_server

published 2d ago modified yesterday also EEF-CVE-2026-123635 , EUVD-2026-125453 , GHSA-7x9q-vvph-rjcr

cvss
6.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 24%
public exploits
0
none known

Summary

Missing Release of Resource after Effective Lifetime vulnerability in elixir-grpc grpc_server allows a client to stall all later calls on a shared HTTP/2 connection via calls that the server refuses while their DATA frames are in flight.

The stream handler grpc_stream_h (grpc_server/src/grpc_stream_h.erl) requests flow from Cowboy only for request data that has arrived. When the server refuses a call early, for example because the body exceeds max_body_size or the method is not implemented, Cowboy drops the DATA frames still in flight for that stream. Their bytes are not returned to the connection flow-control window. After enough refused calls the window is empty. No call on that connection can then send a request body, and each call waits until its deadline. Other connections are not affected.

This issue affects grpc_server: from 1.0.0 before 1.1.0.

Patch / fix

  • hex grpc_server 1.1.0
  • elixir-grpc grpc_server 1.1.0

Is CVE-2026-123635 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Exploit prediction

0.32% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-14).

CVSS scores

assigned by version score vector
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/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

Affected packages

ecosystem package affected fixed in
hex grpc_server
>=1.0.0, <1.1.0
1.1.0

Affected products

  • elixir-grpc grpc_server

Classification

Weakness
  • CWE-772 Missing Release of Resource after Effective Lifetime

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of elixir-grpc/grpc published their own advisory on GitHub. Reviewed sources take precedence over it.