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Fencer Vulns
high 8.3

CVE-2026-63443 json

Coder: Workspace agent API insecure redirect handling allowed cross-agent file read and write

published 2026-07-06 4 mo ago modified 2026-09-30 39 d ago also GHSA-qrwj-vh9x-gw5v , GO-2026-5923 , EUVD-2026-78927

cvss
8.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.8%
EPSS 0.8% chance of exploitation in 30 days, percentile 55%
public exploits
0
none known

Summary

Coder allows organizations to provision remote development environments via Terraform. Prior to 2.29.19, 2.32.9, 2.33.10, and 2.34.4, agentConn.apiClient() follows redirects while its custom transport accepts the host from the redirected request URL when the port is the workspace agent HTTP API port 4. An authenticated user who controls a modified workspace agent and knows another online agent's UUID can derive the victim's tailnet address and redirect control-plane requests to that agent. HTTP 301, 302, and 303 redirects can redirect read requests, while HTTP 307 and 308 preserve replayable write and process-start requests. The redirected workspace agent file APIs can read or write files as the victim workspace user, and affected versions exposing the workspace agent process API can execute commands after a redirected file write, crossing workspace and tenant boundaries. This issue is fixed in versions 2.29.19, 2.32.9, 2.33.10, and 2.34.4.

Patch / fix

  • go github.com/coder/coder/v2 2.29.19, 2.32.9, 2.33.10, 2.34.4

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
54 d ago

Exploit prediction

0.76% chance of exploitation in the next 30 days, higher than 55% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L
GitHub 3.1 8.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L

Affected packages

ecosystem package affected fixed in
go github.com/coder/coder/v2
>=2.34.0, <2.34.4
>=2.33.0, <2.33.10
>=2.30.0, <2.32.9
>=2.27.0, <2.29.19
2.34.4
2.33.10
2.32.9
2.29.19
go github.com/coder/coder
all versions
 no fix listed

Affected products

  • coder coder

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.