Skip to main content

Boteraser | Website and Server Security Solutions

🛡️ CVE-2026-6253 — curl

🟡 CVSS 5.9 — Medium ⚠️ Exploit Public CWE-522 NVD
5.9
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

curl might erroneously pass on credentials for a first proxy to a second

proxy.

This can happen when the following conditions are true:

1. curl is setup to use specific different proxies for different URL schemes

2. the first proxy needs credentials

3. the second proxy uses no credentials

4. while using the first proxy (using say http://), curl is asked to follow

a redirect to a URL using another scheme (say https://), accessed using a

second, different, proxy

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: High — the attacker first has to win a race, learn a secret or otherwise prepare the target.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-6253 is classified as CWE-522: Insufficiently Protected Credentials. Credentials are stored or transmitted with protection too weak for what they unlock.

Affected software

CVE-2026-6253 is recorded against 1 package.

  • curl (from 7.14.1 up to 8.20.0)

Timeline and source

Published on 13 May 2026 and last revised on 17 June 2026. A public exploit is known to exist, which raises the urgency of patching considerably. A vendor advisory or fix has been published. Record sourced from NVD.

References

curl.se
curl.se
hackerone.com
www.openwall.com
hackerone.com

Other advisories for this package

curl has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-522: Insufficiently Protected Credentials) in other software:

Details

Severity MEDIUM
CVSS Score 5.9
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-522
Public Exploit ⚠️ Yes
Source NVD
Published 2026-05-13
Updated 2026-08-20
Modified 2026-06-17

Affected Packages

Software From version Fixed in
curl 7.14.1 8.20.0

References

Exploit, Issue Tracking, Third Party Advisory https://hackerone.com/reports/3669637
Mailing List, Patch, Third Party Advisory http://www.openwall.com/lists/oss-security/2026/04/29/11
Exploit, Issue Tracking, Third Party Advisory https://hackerone.com/reports/3669637

Exploit Protection

Are you running curl?

CVE-2026-6253 carries CVSS 5.9 Medium rating and a public exploit already exists. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

Check My Site For CVE-2026-6253 →

No credit card required  ·  Results in minutes

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

Browse related advisories

All advisoriesCVECVE 2026
✓