CVE-2026-23397

Description

In the Linux kernel, the following vulnerability has been resolved: nfnetlink_osf: validate individual option lengths in fingerprints nfnl_osf_add_callback() validates opt_num bounds and string NUL-termination but does not check individual option length fields. A zero-length option causes nf_osf_match_one() to enter the option matching loop even when foptsize sums to zero, which matches packets with no TCP options where ctx->optp is NULL: Oops: general protection fault KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98) Call Trace: nf_osf_match (net/netfilter/nfnetlink_osf.c:227) xt_osf_match_packet (net/netfilter/xt_osf.c:32) ipt_do_table (net/ipv4/netfilter/ip_tables.c:293) nf_hook_slow (net/netfilter/core.c:623) ip_local_deliver (net/ipv4/ip_input.c:262) ip_rcv (net/ipv4/ip_input.c:573) Additionally, an MSS option (kind=2) with length < 4 causes out-of-bounds reads when nf_osf_match_one() unconditionally accesses optp[2] and optp[3] for MSS value extraction. While RFC 9293 section 3.2 specifies that the MSS option is always exactly 4 bytes (Kind=2, Length=4), the check uses "< 4" rather than "!= 4" because lengths greater than 4 do not cause memory safety issues -- the buffer is guaranteed to be at least foptsize bytes by the ctx->optsize == foptsize check. Reject fingerprints where any option has zero length, or where an MSS option has length less than 4, at add time rather than trusting these values in the packet matching hot path.

CVSS Details

CVSS Score

7.1

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

Linux Kernel < 6.x (需参考具体commit修复版本)

PoC / Exploit Code

⚠ For Security Research Only

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

python

import socket
import struct

# Conceptual PoC to trigger the vulnerability via Netlink
# This script attempts to add a fingerprint with a zero-length option

def send_exploit_netlink_msg():
    # Netlink socket setup
    sock = socket.socket(socket.AF_NETLINK, socket.SOCK_RAW, socket.NETLINK_NETFILTER)
    sock.bind((0, 0))

    # Constructing a malicious fingerprint message
    # Note: This is a simplified representation. Real exploit requires specific NLMSG attributes
    # for OSF fingerprint addition (NFNL_SUBSYS_OSF, OSF_MSG_ADD).
    
    # Malicious data: Option kind 2 (MSS) with length 0 (triggering < 4 check)
    # or a generic option with length 0.
    malicious_option = struct.pack('BB', 2, 0) 
    
    print("[+] Attempting to send malformed fingerprint to kernel...")
    # In a real scenario, construct the full nfnetlink attribute payload here
    # sock.send(nlmsg)
    print("[!] PoC structure generated. Requires kernel with vulnerable nfnetlink_osf.")

if __name__ == "__main__":
    send_exploit_netlink_msg()

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-23397
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-23397
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-23397/
[4] VulDB https://vuldb.com/cve/CVE-2026-23397
[5] https://git.kernel.org/stable/c/224f4678812e1a7bc8341bcb666773a0aec5ea6f
[6] https://git.kernel.org/stable/c/3932620c04c2938c93c0890c225960d3d34ba355
[7] https://git.kernel.org/stable/c/3c11b5c2436a3a5b450612ab160e3a525b28cfb5
[8] https://git.kernel.org/stable/c/4c6aa008b913e808c4f4d3cde36cb1d9bb5967c6
[9] https://git.kernel.org/stable/c/aa0574182c46963c3cdb8cde46ec93aca21100d8
[10] https://git.kernel.org/stable/c/dbdfaae9609629a9569362e3b8f33d0a20fd783c
[11] https://git.kernel.org/stable/c/e9cf17b91e733fec725ebcc0b3098bc5ccd505e0
[12] https://git.kernel.org/stable/c/ec8bf0571b142f29dc0b68ae2ac3952f7a464b38

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-23397", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-03-26T11:16:19.720", "lastModified": "2026-04-24T15:18:09.790", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfnetlink_osf: validate individual option lengths in fingerprints\n\nnfnl_osf_add_callback() validates opt_num bounds and string\nNUL-termination but does not check individual option length fields.\nA zero-length option causes nf_osf_match_one() to enter the option\nmatching loop even when foptsize sums to zero, which matches packets\nwith no TCP options where ctx->optp is NULL:\n\n Oops: general protection fault\n KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]\n RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98)\n Call Trace:\n nf_osf_match (net/netfilter/nfnetlink_osf.c:227)\n xt_osf_match_packet (net/netfilter/xt_osf.c:32)\n ipt_do_table (net/ipv4/netfilter/ip_tables.c:293)\n nf_hook_slow (net/netfilter/core.c:623)\n ip_local_deliver (net/ipv4/ip_input.c:262)\n ip_rcv (net/ipv4/ip_input.c:573)\n\nAdditionally, an MSS option (kind=2) with length < 4 causes\nout-of-bounds reads when nf_osf_match_one() unconditionally accesses\noptp[2] and optp[3] for MSS value extraction. While RFC 9293\nsection 3.2 specifies that the MSS option is always exactly 4\nbytes (Kind=2, Length=4), the check uses \"< 4\" rather than\n\"!= 4\" because lengths greater than 4 do not cause memory\nsafety issues -- the buffer is guaranteed to be at least\nfoptsize bytes by the ctx->optsize == foptsize check.\n\nReject fingerprints where any option has zero length, or where an MSS\noption has length less than 4, at add time rather than trusting these\nvalues in the packet matching hot path."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnfnetlink_osf: validar longitudes de opciones individuales en huellas digitales\n\nnfnl_osf_add_callback() valida los límites de opt_num y la terminación NUL de cadena, pero no verifica los campos de longitud de opciones individuales. Una opción de longitud cero hace que nf_osf_match_one() entre en el bucle de coincidencia de opciones incluso cuando foptsize suma cero, lo que coincide con paquetes sin opciones TCP donde ctx->optp es NULL:\n\n Oops: fallo de protección general\n KASAN: desreferencia de puntero nulo en el rango [0x0000000000000000-0x0000000000000007]\n RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98)\n Traza de llamada:\n nf_osf_match (net/netfilter/nfnetlink_osf.c:227)\n xt_osf_match_packet (net/netfilter/xt_osf.c:32)\n ipt_do_table (net/ipv4/netfilter/ip_tables.c:293)\n nf_hook_slow (net/netfilter/core.c:623)\n ip_local_deliver (net/ipv4/ip_input.c:262)\n ip_rcv (net/ipv4/ip_input.c:573)\n\nAdemás, una opción MSS (tipo=2) con longitud < 4 causa lecturas fuera de límites cuando nf_osf_match_one() accede incondicionalmente a optp[2] y optp[3] para la extracción del valor MSS. Si bien la sección 3.2 de RFC 9293 especifica que la opción MSS es siempre exactamente de 4 bytes (Tipo=2, Longitud=4), la verificación usa '< 4' en lugar de '!= 4' porque las longitudes mayores que 4 no causan problemas de seguridad de la memoria -- el búfer está garantizado para ser de al menos foptsize bytes por la verificación ctx->optsize == foptsize.\n\nRechazar huellas digitales donde cualquier opción tenga longitud cero, o donde una opción MSS tenga longitud menor que 4, en el momento de la adición en lugar de confiar en estos valores en la ruta crítica de coincidencia de paquetes."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H", "baseScore": 7.1, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-125"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.31.1", "versionEndExcluding": "5.10.253", "matchCriteriaId": "57E89197-6305-4D47-AE24-4D5D20CC8429"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.203", "matchCriteriaId": "20DDB3E9-AABF-4107-ADB0-5362AA067045"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.167", "matchCriteriaId": "2EDC6BAF-B710-4E26-B6AA-D68922E ... (truncated)