CVE-2026-55438

MEDIUMNVD 6.86.8—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.8 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 88% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
6.8EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 6.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2, Coder's subdomain-based workspace app proxy allowed the same-owner CORS check to be bypassed. When a workspace-name subdomain segment parsed as a UUID, the workspace was resolved by ID without confirming the URL's username matched the real owner, while the CORS middleware trusted the unverified username in the hostname. Practical exploitation requires subdomain app routing (wildcard hostname) enabled and a victim who visits the attacker's crafted app URL while authenticated. The fix in versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2 validates the subdomain username against the resolved workspace's actual owner and bases the same-owner CORS decision on the authoritative owner identity. No known workarounds are available.

CVSS v3
6.8
EG Score
6.8MEDIUMmedium confidence
EG Risk
31
EG Risk 31/100

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity68% × 45%
Exploitation0% × 40%
Automatability0% × 15%
EPSS PROB
0.2%
EPSS %ILE
11th
KEV
Not listed

Published

July 6, 2026

Last Modified

July 8, 2026

Advisory Details (7)

Auto-updated Jul 8, 2026
Patch available. Sources: github_pr, github_release, github.
githubMentions a patch (unverified)

Workspace app CORS origin check can be bypassed via UUID-based subdomain spoofing · Advisory · coder/coder · GitHub

https://github.com/coder/coder/security/advisories/GHSA-5wg6-jmq2-53pw
github_release Patch Available

v2.34.2 [SECURITY]

Patch available: coder/coder v2.34.2

https://github.com/coder/coder/releases/tag/v2.34.2
github_release Patch Available

v2.33.8 [SECURITY]

Patch available: coder/coder v2.33.8

https://github.com/coder/coder/releases/tag/v2.33.8
github_release Patch Available

v2.32.7 [SECURITY]

Patch available: coder/coder v2.32.7

https://github.com/coder/coder/releases/tag/v2.32.7
github_release Patch Available

v2.29.17 [SECURITY]

Patch available: coder/coder v2.29.17

https://github.com/coder/coder/releases/tag/v2.29.17
github_pr

fix: base workspace-app CORS on resolved owner instead of URL username

Upstream fix in progress (PR #26086 · coder/coder, state=closed)

https://github.com/coder/coder/pull/26086
github_pr

fix(coderd/workspaceapps): verify workspace owner matches app username

Fix merged in coder/coder PR #26085 on 2026-06-10 — awaiting tagged release

https://github.com/coder/coder/pull/26085

Vendor Advisories for CVE-2026-55438(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(2 across 1 ecosystem)
Go(2)
PackageVulnerable rangeFix by version rangeDependents
github.com/coder/coder—
  • every version on: no fix on record
—
github.com/coder/coder/v2—
  • 2.34.0 up to 2.34.2: fixed in 2.34.2
  • 2.33.0 up to 2.33.8: fixed in 2.33.8
  • 2.30.0 up to 2.32.7: fixed in 2.32.7
  • every version up to 2.29.17: fixed in 2.29.17
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 31× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 125 total refreshes for this CVE.

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Frequently asked(5)

What is CVE-2026-55438?
CVE-2026-55438 is a medium vulnerability published on July 6, 2026. Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2, Coder's subdomain-based workspace app proxy allowed the same-owner CORS check to be bypassed. When a workspace-name subdomain segment parsed as a UUID, the…
When was CVE-2026-55438 disclosed?
CVE-2026-55438 was first published on July 6, 2026, with the most recent update on July 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55438 actively exploited?
CVE-2026-55438 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (11th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55438?
CVE-2026-55438 has a CVSS v3 base score of 6.8 (NVD).
How do I remediate CVE-2026-55438?
A fix for CVE-2026-55438 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55438 are linked in the Vendor Advisories panel on this page.

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