CVE-2023-26483: gosaml2 vulnerable to Denial of Service via deflate decompression bomb

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-03-03 · updated 2026-06-17
Weakness: CWE-409

Description

gosaml2 is a Pure Go implementation of SAML 2.0. SAML Service Providers using this library for SAML authentication support are likely susceptible to Denial of Service attacks. A bug in this library enables attackers to craft a `deflate`-compressed request which will consume significantly more memory during processing than the size of the original request. This may eventually lead to memory exhaustion and the process being killed. The maximum compression ratio achievable with `deflate` is 1032:1, so by limiting the size of bodies passed to gosaml2, limiting the rate and concurrency of calls, and ensuring that lots of memory is available to the process it _may_ be possible to help Go's garbage collector "keep up". Implementors are encouraged not to rely on this. This issue is fixed in version 0.9.0.

Affected products

russellhaering gosaml2: before 0.9.0 — fixed in 0.9.0

How to fix

Upgrade to a fixed version: russellhaering gosaml2 0.9.0. Check the vendor advisory for mitigations.

References

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