CVE-2025-39880: libceph: fix invalid accesses to ceph_connection_v1_info

Vulnerability summary

CVE-2025-39880 is a critical (CVSS 9.8) Incorrect Type Conversion or Cast vulnerability in debian debian_linux. EPSS estimates a 0.33% chance of exploitation in the next 30 days, higher than 26.2% of scored vulnerabilities.

Timeline

1. 23-09-2025
   PublishedVulnerability first disclosed.
2. 15-10-2026
   Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: libceph: fix invalid accesses to ceph_connection_v1_info There is a place where generic code in messenger.c is reading and another place where it is writing to con->v1 union member without checking that the union member is active (i.e. msgr1 is in use). On 64-bit systems, con->v1.auth_retry overlaps with con->v2.out_iter, so such a read is almost guaranteed to return a bogus value instead of 0 when msgr2 is in use. This ends up being fairly benign because the side effect is just the invalidation of the authorizer and successive fetching of new tickets. con->v1.connect_seq overlaps with con->v2.conn_bufs and the fact that it's being written to can cause more serious consequences, but luckily it's not something that happens often.

• CWE-704Incorrect Type Conversion or CastThe product does not correctly convert an object, resource, or structure from one type to a different type.