CVE-2026-87864
Description
A flaw was found in curl. When curl is configured to perform carriage return and line feed (CRLF) conversion during an Internet Message Access Protocol (IMAP) append operation, it incorrectly reports the raw input size rather than the expanded byte count. Because the receiving server only reads the advertised length as message data, it interprets the remaining overflow bytes as subsequent commands. An attacker capable of supplying message data with line breaks can exploit this issue to execute unauthorized IMAP commands within an authenticated session.
Statement
Red Hat has evaluated this vulnerability as Low impact because exploitation demands an atypical configuration combining IMAP message uploads with explicit line-ending conversions. Furthermore, a malicious actor must have the ability to supply crafted message content within an established, authenticated mailbox session to trigger command pipelining. In standard Red Hat Enterprise Linux environments, libcurl client applications do not enable CRLF conversion by default, significantly constraining the practical attack surface.
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 | 3.7 | N/A | N/A |
| Attack Vector | Network | N/A | N/A |
| Attack Complexity | High | N/A | N/A |
| Privileges Required | Low | N/A | N/A |
| User Interaction | Required | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | Low | N/A | N/A |
| Integrity Impact | Low | N/A | N/A |
| Availability Impact | None | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N
Understanding the Weakness (CWE)
Confidentiality,Integrity
Technical Impact: Read Memory; Modify Memory; Varies by Context
Acknowledgements
Red Hat would like to thank Stanislav Fort (Aisle Research) for reporting this issue.
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