How severe is CVE-2026-55079?

CVE-2026-55079 has a CVSS score of 4.9/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-55079?

CVE-2026-55079 affects the following packages: github.com/coder/coder/v2 (Go), github.com/coder/coder/v2 (Go), github.com/coder/coder/v2 (Go), github.com/coder/coder/v2 (Go). Ecosystems affected: Go.

How do I fix CVE-2026-55079?

Update github.com/coder/coder/v2 to 2.34.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55079 is resolved across your whole dependency graph.

How do I detect CVE-2026-55079 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/coder/coder/v2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-55079 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-55079 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-55079 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-55079?

CVE-2026-55079 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 49th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-55079?

CVE-2026-55079 is classified as CWE-789 (CWE-789). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-55079 published, and has it been updated?

CVE-2026-55079 was published on July 7, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

MEDIUM severity

CVE-2026-55079 — coder

MEDIUMFix: coder/coder#25710

CVE-2026-55079 is a medium-severity (CVSS 4.9) CWE-789 vulnerability in github.com/coder/coder/v2. A fix is available for github.com/coder/coder/v2 — see the affected versions and patch details below.

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

Also known asGHSA-f962-qm93-mj4cGO-2026-5911

Published

Jul 7, 2026

Updated

Oct 21, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

None indexed

Exploitation data as of Oct 24, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-55079.

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs49th percentile — riskier than 49% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-55079 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,308 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

4 pkgs affected

🐹github.com/coder/coder/v2🐹github.com/coder/coder/v2🐹github.com/coder/coder/v2🐹github.com/coder/coder/v2

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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

Credits

Coder would like to thank Anthropic's Security Team (ANT-2026-22442) for independently disclosing this issue!

Affected Packages

4 total 4 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/coder/coder/v2`	≥ 2.34.0&&< 2.34.2	2.34.2`go get github.com/coder/coder/v2@v2.34.2`
🐹Go	`github.com/coder/coder/v2`	≥ 2.33.0&&< 2.33.8	2.33.8`go get github.com/coder/coder/v2@v2.33.8`
🐹Go	`github.com/coder/coder/v2`	≥ 2.30.0&&< 2.32.7	2.32.7`go get github.com/coder/coder/v2@v2.32.7`
🐹Go	`github.com/coder/coder/v2`	≥ 2.24.0&&< 2.29.17	2.29.17`go get github.com/coder/coder/v2@v2.29.17`

Affected Products

1 product · 4 configurations

Application

codercoder

≥ 2.34.0 && < 2.34.2

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/coder/coder/v2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/coder/coder/v2 to 2.34.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55079 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

### 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.