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.
"}]}], "references": [{"url": "https://github.com/temporalio/tchannel-go/commit/8d8ca17342b3620d3a6d5c1a825145595e7588ff", "name": "First affected source revision", "tags": ["product"]}, {"url": "https://github.com/temporalio/tchannel-go/blob/8706a1ab5f617efd79dace7ab2d1d80cc1881df0/fragmenting_reader.go#L256-L308", "name": "Vulnerable zero-chunk fragment handling", "tags": ["product"]}, {"url": "https://github.com/temporalio/tchannel-go/commit/1dcfa67262ecd56a24f12940f4082549190cb5d1", "name": "Direct inbound call route", "tags": ["product"]}, {"url": "https://github.com/temporalio/tchannel-go/pull/14", "name": "Zero-chunk fragment validation fix", "tags": ["patch"]}, {"url": "https://github.com/temporalio/tchannel-go/commit/0cb017f6870a8420695abeb9a4560d39dadc4e2e", "name": "First fixed source revision", "tags": ["patch"]}, {"url": "https://github.com/temporalio/tchannel-go/tree/v1.22.1", "name": "Fixed release tag v1.22.1", "tags": ["product"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "temporalio/tchannel-go reasonable worst-case network service embedding"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "version": "4.0", "baseSeverity": "HIGH", "baseScore": 8.7, "vectorString": "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"}}], "configurations": [{"lang": "en", "value": "The CVSS Base score reflects an application that exposes a tchannel-go listener to untrusted network peers without an authenticated transport. The library accepts caller-supplied listeners and dialers, so an embedding application can require mutually authenticated TLS. When client certificates are required and verified, unauthenticated peers are rejected before TChannel frame parsing and the deployment should be assessed using appropriate Environmental metrics.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "The CVSS Base score reflects an application that exposes a tchannel-go listener to untrusted network peers without an authenticated transport. The library accepts caller-supplied listeners and dialers, so an embedding application can require mutually authenticated TLS. When client certificates are required and verified, unauthenticated peers are rejected before TChannel frame parsing and the deployment should be assessed using appropriate Environmental metrics.
"}]}], "workarounds": [{"lang": "en", "value": "Restrict TChannel listener access to trusted peers. Where supported by the embedding application, require mutually authenticated TLS so peers without a trusted client certificate are rejected before TChannel frame parsing. External panic-recovery middleware is not a reliable mitigation because the confirmed inbound panic occurs on a library-created dispatch goroutine.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "Restrict TChannel listener access to trusted peers. Where supported by the embedding application, require mutually authenticated TLS so peers without a trusted client certificate are rejected before TChannel frame parsing. External panic-recovery middleware is not a reliable mitigation because the confirmed inbound panic occurs on a library-created dispatch goroutine.
"}]}], "solutions": [{"lang": "en", "value": "Upgrade github.com/temporalio/tchannel-go to v1.22.1 or later. The fix rejects fragments containing no argument chunks before indexing the chunk slice.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "Upgrade github.com/temporalio/tchannel-go to v1.22.1 or later. The fix rejects fragments containing no argument chunks before indexing the chunk slice.
"}]}], "credits": [{"lang": "en", "value": "An external security researcher who reported this issue responsibly to Temporal Technologies", "type": "finder"}], "source": {"discovery": "EXTERNAL"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-09-21T15:28:04.791087Z", "id": "CVE-2026-65653", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-09-21T15:28:21.825Z"}}]}}