CVE-2026-4873
Description
A flaw was found in curl. A remote attacker could exploit this by initiating an unencrypted connection (via IMAP, SMTP, or POP3) and then making a subsequent request to the same host that requires Transport Layer Security (TLS). Due to incorrect connection reuse, the subsequent request would bypass the TLS requirement, leading to the transmission of sensitive information in cleartext. This vulnerability, categorized as Cleartext Transmission of Sensitive Information (CWE-319), results in information disclosure.
Statement
Moderate: This flaw in curl allows for information disclosure when an unencrypted connection is incorrectly reused for a subsequent request that expects TLS. This can lead to the cleartext transmission of sensitive data, potentially affecting Red Hat products that utilize curl for IMAP, SMTP, or POP3 connections where connection reuse is enabled.
Mitigation
To mitigate this issue, avoid using clear-text IMAP, POP3, or SMTP transfers with curl. Ensure that all connections for these protocols are initiated with TLS from the outset to prevent the reuse of unencrypted connections.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.3 | N/A | 5.9 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Understanding the Weakness (CWE)
Integrity,Confidentiality
Technical Impact: Read Application Data; Modify Files or Directories
Anyone can read the information by gaining access to the channel being used for communication. Many communication channels can be "sniffed" (monitored) by adversaries during data transmission. For example, in networking, packets can traverse many intermediary nodes from the source to the destination, whether across the internet, an internal network, the cloud, etc. Some actors might have privileged access to a network interface or any link along the channel, such as a router, but they might not be authorized to collect the underlying data. As a result, network traffic could be sniffed by adversaries, spilling security-critical data.
Integrity,Confidentiality
Technical Impact: Read Application Data; Modify Files or Directories; Other
When full communications are recorded or logged, such as with a packet dump, an adversary could attempt to obtain the dump long after the transmission has occurred and try to "sniff" the cleartext from the recorded communications in the dump itself. Even if the information is encoded in a way that is not human-readable, certain techniques could determine which encoding is being used, then decode the information.
Frequently Asked Questions
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