🛡️ CVE-2026-55078 — coder

🟡 CVSS 6.5 — Medium ✅ No Known Exploit CWE-409 NVD
6.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Coder: Zip upload decompression lacks aggregate size limit, enabling denial of service

Summary

POST /api/v2/files converts zip uploads to tar in memory via CreateTarFromZip, which enforced a per-entry size limit but no aggregate limit on total decompressed output, writing to an unbounded in-memory buffer.

> Note: Exploitation requires authenticated file-upload access and the impact is limited to availability (denial of service).

Impact

An authenticated user could upload a zip within the 100 MiB upload limit but containing many highly compressible entries whose decompressed size exhausted memory, crashing coderd before any RBAC check. Repeated requests could keep the service unavailable. This is a denial of service; it does not allow data disclosure or code execution.

Patches

The fix adds a metadata preflight check that sums projected entry sizes and a streaming writer that enforces the aggregate limit during decompression.

The fix was backported to all supported release lines:

| Release line | Patched version |

|---|---|

| 2.34 | [v2.34.2](https://github.com/coder/coder/releases/tag/v2.34.2) |

| 2.33 | [v2.33.8](https://github.com/coder/coder/releases/tag/v2.33.8) |

| 2.32 | [v2.32.7](https://github.com/coder/coder/releases/tag/v2.32.7) |

| 2.29 (ESR) | [v2.29.17](https://github.com/coder/coder/releases/tag/v2.29.17) |

Workarounds

Restrict file-upload permissions to trusted users or place a reverse proxy with request-body size limits in front of coderd.

Resources

  • Fix: #25877

Credits

Coder would like to thank Anthropic's Security Team (ANT-2026-22438) for independently disclosing this issue!

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level 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.

Affected software

CVE-2026-55078 is recorded against 3 packages.

  • coder (from 2.34.0 up to 2.34.2)
  • github.com/coder/coder
  • github.com/coder/coder/v2

Timeline and source

Published on 7 July 2026 and last revised on 8 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com
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github.com
github.com
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Details

Severity MEDIUM
CVSS Score 6.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CWE CWE-409
Public Exploit ✅ No
Source NVD
Published 2026-07-07
Updated 2026-08-12
Modified 2026-07-08

Affected Packages

Software From version Fixed in
coder 2.34.0 2.34.2
github.com/coder/coder — —
github.com/coder/coder/v2 — —

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