CVE-2026-50285 Pomerium: Pre-Auth Memory Exhaustion via Unbounded zstd Decompression in HPKE Callback
Unauthenticated attackers can cause memory exhaustion and service disruption in Pomerium stateless deployments via unbounded zstd decompression.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-50285?
CVE-2026-50285 is a high-severity denial of service vulnerability in pomerium, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-50285?
2 open source packages ship an affected version, including github.com/pomerium/pomerium.
| Package | Affected | Fixed in |
|---|---|---|
github.com/pomerium/pomerium Go | From 0.32.6 | 0.32.8 |
github.com/pomerium/pomerium Go | From 0.32.6 | 0.32.8 |
How do I fix CVE-2026-50285?
Upgrade github.com/pomerium/pomerium to 0.32.8 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-50285 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-50285 exists.
Sources
Also known as GHSA-ggw3-5987-rx77.