What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-17 · updated 2026-09-24
• Weakness: CWE-770

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.

Affected products

• pomerium: before 0.32.8

References

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

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