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Description

During session resumption in crypto/tls, if the underlying Config has its ClientCAs or RootCAs fields mutated between the initial handshake and the resumed handshake, the resumed handshake may succeed when it should have failed. This may happen when a user calls Config.Clone and mutates the returned Config, or uses Config.GetConfigForClient. This can cause a client to resume a session with a server that it would not have resumed with during the initial handshake, or cause a server to resume a session with a client that it would not have resumed with during the initial handshake.

PUBLISHED Reserved 2025-12-15 | Published 2026-02-05 | Updated 2026-02-06 | Assigner Go

Problem types

CWE-295: Improper Certificate Validation

Product status

Default status
unaffected

Any version before 1.24.13
affected

1.25.0-0 (semver) before 1.25.7
affected

1.26.0-rc.1 (semver) before 1.26.0-rc.3
affected

Credits

Coia Prant (github.com/rbqvq)

Go Security Team

References

groups.google.com/g/golang-announce/c/K09ubi9FQFk

go.dev/cl/737700

go.dev/issue/77217

pkg.go.dev/vuln/GO-2026-4337

cve.org (CVE-2025-68121)

nvd.nist.gov (CVE-2025-68121)

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