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Medium, CVSS 4.9

Coder's unbounded memory allocation in provisioner file upload allows authenticated denial of service

CVE-2026-55079GHSA-f962-qm93-mj4c

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/coder/coder/v2 2.34.2, 2.33.8, 2.32.7, 2.29.17), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Go github.com/coder/coder/v2

    Affected
    >= 2.34.0, < 2.34.2>= 2.33.0, < 2.33.8>= 2.30.0, < 2.32.7>= 2.24.0, < 2.29.17
    Fixed in
    2.33.8, 2.29.17, 2.34.2, 2.32.7

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
4.9 · CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
EPSS
  • CVE-2026-55079: 0.61% estimated exploitation activity in the next 30 days; percentile 49.30 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary NewDataBuilder in provisionersdk/proto/dataupload.go allocated a byte slice using the client-supplied FileSize from a DataUpload message without an upper-bound check. Although the DRPC wire limit is 4 MiB, the FileSize value itself was unconstrained Impact An authenticated user able to reach the provisioner daemon serve endpoint could send a roughly 50-byte message declaring a huge FileSize (for example 1 TiB), triggering an unrecoverable Go out-of-memory abort that terminates coderd. This is a single-message denial of service affecting the entire deployment. Patches The fix validates FileSize against an upper bound (MaxFileSize = 100 MiB) before allocation. The fix was backported to all supported release lines: | Release line | Patched version | |---|---| | 2.34 | v2.34.2 | | 2.33 | v2.33.8 | | 2.32 | v2.32.7 | | 2.29 (ESR) | v2.29.17 | Workarounds Restrict access to the provisioner daemon serve endpoint to trusted provisioner daemon service accounts. Resources - Fix: #25710…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-f962-qm93-mj4c

Agent brief

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# Patch Next advisory brief: CVE-2026-55079

Advisory: Coder's unbounded memory allocation in provisioner file upload allows authenticated denial of service
IDs: CVE-2026-55079, GHSA-f962-qm93-mj4c
Record: https://patchnext.com/advisories/cve-2026-55079 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/coder/coder/v2 2.34.2, 2.33.8, 2.32.7, 2.29.17. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/coder/coder/v2: affected >= 2.34.0, < 2.34.2; >= 2.33.0, < 2.33.8; >= 2.30.0, < 2.32.7; >= 2.24.0, < 2.29.17; fixed in 2.33.8, 2.29.17, 2.34.2, 2.32.7

## Suggested inspection (read-only)
- Go github.com/coder/coder/v2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/coder/coder/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-f962-qm93-mj4c (GitHub-reviewed advisory GHSA-f962-qm93-mj4c lists affected ranges: Go github.com/coder/coder/v2 >=2.34.0 =2.33.0 =2.30.0 =2.24.0 <2.29.17)

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