🛡️ CVE-2026-54638 — td

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-770 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

Weakness class

CVE-2026-54638 is classified as CWE-770: Allocation of Resources Without Limits. Resources are allocated on request with no cap, so a client can exhaust them.

Affected software

CVE-2026-54638 is recorded against 2 packages.

  • github.com/gotd/td
  • unknown

Timeline and source

Published on 28 July 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com (Web)
github.com (Web)
github.com (Web)
github.com (Package)
github.com (Web)

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-770
Public Exploit ✅ No
Source NVD
Published 2026-07-28
Updated 2026-08-12
Modified 2026-07-28
Fix URL N/A

Affected Packages

Software From version Fixed in
github.com/gotd/td — —
unknown — —

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