Pomerium Pre-Auth Memory Exhaustion via Unbounded zstd Decompression in HPKE Callback

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-50285: 0.74% estimated exploitation activity in the next 30 days; percentile 54.68 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The HPKE V2 URL decode path in pkg/hpke/url.go decompresses attacker-controlled zstd data without any size limit. On Pomerium deployments using the stateless authentication flow (Pomerium Zero / hosted authenticate), the proxy's /.pomerium/callback endpoint is reachable without credentials and processes attacker-crafted HPKE-encrypted payloads before the sender's identity is validated. Because Pomerium's HPKE receiver public key is publicly served, an attacker can encrypt a decompression bomb, deliver it to the callback endpoint, and cause unbounded memory allocation — crashing or degrading the proxy process. Severity High (CVSS 3.1: 7.5) CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Attack Vector: Network — the /.pomerium/callback route on the proxy service is externally reachable. - Attack Complexity: Low — the receiver public key is publicly available at /.well-known/pomerium/hpke-public-key; no special conditions apply. - Privileges Required: None — the callback endpoint…

Published by the source

15 Jul 2026, 23:08 UTC

Last modified by the source

15 Jul 2026, 23:08 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-ggw3-5987-rx77

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# Patch Next advisory brief: CVE-2026-50285

Advisory: Pomerium Pre-Auth Memory Exhaustion via Unbounded zstd Decompression in HPKE Callback
IDs: CVE-2026-50285, GHSA-ggw3-5987-rx77
Record: https://patchnext.com/advisories/cve-2026-50285 (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: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/pomerium/pomerium 0.32.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/pomerium/pomerium: affected >= 0.32.6, < 0.32.8; fixed in 0.32.8

## Suggested inspection (read-only)
- Go github.com/pomerium/pomerium: 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/pomerium/pomerium.
- 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-ggw3-5987-rx77 (GitHub-reviewed advisory GHSA-ggw3-5987-rx77 lists affected ranges: Go github.com/pomerium/pomerium >=0.32.6 <0.32.8)

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