td has pre-auth denial of service via unbounded memory allocation in proto.UnencryptedMessage.Decode

### Impact A remote, unauthenticated attacker can cause excessive memory allocation (and resulting CPU / GC pressure, potentially OOM termination) by sending a crafted unencrypted MTProto packet. `(*proto.UnencryptedMessage).Decode` read an attacker-controlled 32-bit `dataLen` field and immediately allocated a buffer of that size via `make([]byte, dataLen)` **before** validating that the underlying buffer actually contained that many bytes. A 20-byte packet declaring a ~1.75 GB payload (e.g. `dataLen = 0x70000000`) forces the runtime to provision and zero-initialize a multi-gigabyte heap allocation before the length is rejected. Unencrypted messages are part of the unauthenticated MTProto handshake path, so no credentials or established session are required to reach the vulnerable code. Impact is limited to availability; there is no evidence of memory corruption, out-of-bounds access, or code execution. ### Patches Fixed in **v0.145.1** by validating `dataLen` against the remaining buffer length before allocation (commit `9d5d1f31e`). ### Workarounds Upgrade to v0.145.1 or later. There is no in-process workaround for affected versions short of avoiding exposure of the unauthenticated MTProto parsing path to untrusted peers.

Source published

28 Jul 2026 22:15:28 UTC

Source modified

18 Aug 2026 17:24:12 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH