Vulnerability · Published May 13, 2026 · Assigned by curl
CVE-2026-4873connection reuse ignores TLS requirement
Medium 5.9
In plain English
A medium-severity security flaw in curl from curl. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 26% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)5.9Medium
Exploit odds (30 days)0.3%top 73.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.21 | curl | 8.14.1-r3 | ALPINE-CVE-2026-4873 |
| Alpine:v3.22 | curl | 8.14.1-r4 | ALPINE-CVE-2026-4873 |
| Alpine:v3.23 | curl | 8.20.0-r0 | ALPINE-CVE-2026-4873 |
| Alpine:v3.24 | curl | 8.20.0-r0 | ALPINE-CVE-2026-4873 |
| Debian:12 | curl | no fix listed | DEBIAN-CVE-2026-4873 |
| Debian:13 | curl | 8.14.1-2+deb13u4 | DEBIAN-CVE-2026-4873 |
| Debian:14 | curl | 8.20.0~rc2-1 | DEBIAN-CVE-2026-4873 |
| Ubuntu:22.04:LTS | curl | 7.81.0-1ubuntu1.24 | UBUNTU-CVE-2026-4873 |
| Ubuntu:24.04:LTS | curl | 8.5.0-2ubuntu10.9 | UBUNTU-CVE-2026-4873 |
| Ubuntu:25.10 | curl | 8.14.1-2ubuntu1.3 | UBUNTU-CVE-2026-4873 |
| Ubuntu:26.04:LTS | curl | 8.18.0-1ubuntu2.1 | UBUNTU-CVE-2026-4873 |
Affected products (as reported)
Weakness: CWE-319 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N