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🛡️ CVE-2026-4873 — curl

🟡 CVSS 5.9 — Medium ⚠️ Exploit Public CWE-295 NVD
5.9
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

A vulnerability exists where a connection requiring TLS incorrectly reuses an

existing unencrypted connection from the same connection pool. If an initial

transfer is made in clear-text (via IMAP, SMTP, or POP3), a subsequent request

to that same host bypasses the TLS requirement and instead transmit data

unencrypted.

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 high, integrity none, availability none.

CVSS metrics in full

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

  • 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: High — total loss, or loss the attacker controls.
  • Integrity impact: None.
  • Availability impact: None.

Weakness class

CVE-2026-4873 is classified as CWE-295: Improper Certificate Validation. A TLS certificate is accepted without proper verification, so a man-in-the-middle can present their own.

Affected software

CVE-2026-4873 is recorded against 1 package.

  • curl (from 7.20.0 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

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-295: Improper Certificate Validation) 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:H/I:N/A:N
CWE CWE-295
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 7.20.0 8.20.0

References

Exploit, Issue Tracking, Third Party Advisory https://hackerone.com/reports/3621851
Mailing List, Patch, Third Party Advisory http://www.openwall.com/lists/oss-security/2026/04/29/7

Exploit Protection

Are you running curl?

CVE-2026-4873 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.

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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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