CVE-2026-4873 connection reuse ignores TLS requirement
Attackers can intercept unencrypted data when curl incorrectly reuses a clear-text connection for a TLS-required request, affecting applications using the library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-4873?
CVE-2026-4873 is a medium-severity vulnerability in Haxx Curl, published on 13 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Which versions are affected by CVE-2026-4873?
It affects 1 product.
Products include Haxx Curl.
How do I fix CVE-2026-4873?
Upgrade to a fixed version.
Is CVE-2026-4873 being exploited?
There is no known exploitation of CVE-2026-4873 in the wild and no public exploit code.
Other vulnerabilities in Haxx Curl
Sources
Also known as ALPINE-CVE-2026-4873, AZL-86658, AZL-86685, BELL-CVE-2026-4873, CURL-CVE-2026-4873, DEBIAN-CVE-2026-4873 and 8 more.