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🛡️ JLSEC-2026-1206 — curl-jll (CVE-2026-6253)

⚪ Unknown ✅ No Known Exploit OSV
N/A
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.

Affected software

JLSEC-2026-1206 is recorded against 2 packages.

  • curl-jll
  • libcurl-jll

Timeline and source

Published on 7 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

www.openwall.com (Web)
curl.se (Web)
curl.se (Web)
hackerone.com (Web)

Other advisories for this package

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

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-08-07
Updated 2026-08-20
Modified 2026-08-07
Fix URL N/A

Affected Packages

Software From version Fixed in
curl-jll — —
libcurl-jll — —

Similar Threats

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ⓘ 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.

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