CVE-2026-80558 in Linux
Summary
by MITRE • 08/26/2026
In the Linux kernel, the following vulnerability has been resolved:
libceph: Avoid using invalid osd indices from primary_temp
A corrupted osdmap received from a Ceph monitor or OSD may contain osd indices in its pg_temp, primary_temp, pg_upmap, and pg_upmap_items parts that don't exist, i.e., that are greater than max_osd or smaller than CEPH_HOMELESS_OSD (-1). These indices are used to create the up and acting set in ceph_pg_to_up_acting_osds(), called from calc_target(). While most of these osd indices are checked, the one from primary_temp is not. Subsequently, this may lead to calc_target() returning this (potentially invalid) index as target osd for a (linger) request. Because the osd_state, osd_weight, and osd_addr arrays only contain max_osd entries (with indices 0 to max_osd -1), this leads to out-of-bounds accesses when trying to read values from these arrays.
This patch fixes the issue by adding a check to get_temp_osds(), so that only valid osd indices from primary_temp are used, and it falls back to using the primary from pg_temp or the up set if it is invalid.
[ idryomov: changelog ]
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Analysis
by VulDB Data Team • 08/26/2026
The Linux kernel's Ceph distributed storage client contains a critical input validation flaw within its object placement logic that can lead to out-of-bounds memory access and potential system instability. This vulnerability arises from the handling of metadata received from Ceph monitors or OSDs, specifically concerning the osdmap structure which defines cluster topology and data distribution rules. The core issue lies in how invalid Object Storage Device indices are processed during the calculation of target OSDs for I/O requests. When a corrupted or maliciously crafted osdmap is transmitted to the client, it may contain entries in the primary_temp section that reference OSD identifiers outside the valid range defined by max_osd or below CEPH_HOMELESS_OSD. While other sections like pg_temp and up sets undergo rigorous validation checks before being used, the primary_temp indices were previously passed through without sufficient boundary verification.
The technical mechanism of this flaw centers on the ceph_pg_to_up_acting_osds function which is invoked by calc_target to determine where data should be written or read. This function relies on arrays such as osd_state, osd_weight, and osd_addr that are allocated with a fixed size corresponding strictly to max_osd entries indexed from zero to max_osd minus one. If an invalid index greater than or equal to max_osd is extracted from primary_temp and used without validation, the subsequent array access operations will exceed the bounds of these memory structures. This results in out-of-bounds reads which can corrupt kernel heap data, leak sensitive information contained within adjacent memory regions, or cause a kernel panic due to accessing unmapped physical addresses depending on the specific memory layout at runtime.
From an operational perspective, this vulnerability poses significant risks to system availability and integrity. An attacker with the ability to manipulate network traffic between Ceph monitors and clients could inject malformed osdmap data to trigger these out-of-bounds accesses remotely. Such exploitation can lead to denial of service conditions by crashing the kernel or potentially allow for arbitrary code execution if the memory corruption is carefully crafted to overwrite function pointers or control flow structures. The impact extends beyond immediate system failure as it undermines the reliability guarantees expected from distributed storage systems, where consistent and correct data placement is paramount.
This vulnerability aligns with CWE-125 Out-of-bounds Read in terms of its technical classification, reflecting the improper limitation upon array indexing that allows access to memory outside intended boundaries. It also relates to CWE-20 Improper Input Validation as the root cause is the failure to adequately sanitize and verify external data before processing it within critical kernel logic. In the context of MITRE ATT&CK techniques, this flaw could be leveraged for Defense Evasion or Privilege Escalation if exploited in conjunction with other vulnerabilities, although its primary immediate impact falls under Impact categories such as Denial of Service due to system crash or instability.
The resolution involves modifying the get_temp_osds function within the libceph module to enforce strict validation on indices derived from primary_temp before they are utilized for target selection logic. By implementing checks that ensure any OSD index is both non-negative and strictly less than max_osd, the kernel prevents invalid references from propagating into array access operations. If an index fails these validity checks, the system gracefully falls back to using alternative sources such as the standard primary set from pg_temp or the up set, thereby maintaining operational continuity without compromising memory safety. This patch effectively closes the gap in input validation that allowed corrupted metadata to trigger unsafe memory accesses within the kernel space.