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CVE-2026-23397— nfnetlink_osf: validate individual option lengths in fingerprints

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于未验证指纹中单个选项的长度，可能导致空指针取消引用和越界读取。

AI Predicted 6.5 Difficulty: Moderate EPSS 0.12% · P2

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384< e9cf17b91e733fec725ebcc0b3098bc5ccd505e0 affected
11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384< 3c11b5c2436a3a5b450612ab160e3a525b28cfb5 affected
11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384< aa0574182c46963c3cdb8cde46ec93aca21100d8 affected
11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384< 224f4678812e1a7bc8341bcb666773a0aec5ea6f affected
11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384< ec8bf0571b142f29dc0b68ae2ac3952f7a464b38 affected
11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384< 3932620c04c2938c93c0890c225960d3d34ba355 affected
11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384< 4c6aa008b913e808c4f4d3cde36cb1d9bb5967c6 affected
11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384< dbdfaae9609629a9569362e3b8f33d0a20fd783c affected
… +10 more rows
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I. Basic Information for CVE-2026-23397

Vulnerability Information
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Vulnerability Title
nfnetlink_osf: validate individual option lengths in fingerprints
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于未验证指纹中单个选项的长度，可能导致空指针取消引用和越界读取。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 11eeef41d5f63c7d2f7fdfcc733eb7fb137cc384 ~ e9cf17b91e733fec725ebcc0b3098bc5ccd505e0 -
Linux Linux 2.6.31 -

II. Public POCs for CVE-2026-23397

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III. Intelligence Information for CVE-2026-23397

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Patches & Fixes for CVE-2026-23397 (6)

Same Patch Batch · Linux · 2026-03-26 · 3 CVEs total

CVE-2026-23398 icmp: fix NULL pointer dereference in icmp_tag_validation()
CVE-2026-23396 wifi: mac80211: fix NULL deref in mesh_matches_local()

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-23397

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