Critical severity · published Jun 24, 2026
CVE-2026-52999
netfilter: nfnetlink_osf: fix out-of-bounds read on option matching
9.1
CVSS
0.6%
EPSS
No
On KEV
Description
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nfnetlink_osf: fix out-of-bounds read on option matching
In nf_osf_match(), the nf_osf_hdr_ctx structure is initialized once
and passed by reference to nf_osf_match_one() for each fingerprint
checked. During TCP option parsing, nf_osf_match_one() advances the
shared ctx->optp pointer.
If a fingerprint perfectly matches, the function returns early without
restoring ctx->optp to its initial state. If the user has configured
NF_OSF_LOGLEVEL_ALL, the loop continues to the next fingerprint.
However, because ctx->optp was not restored, the next call to
nf_osf_match_one() starts parsing from the end of the options buffer.
This causes subsequent matches to read garbage data and fail
immediately, making it impossible to log more than one match or logging
incorrect matches.
Instead of using a shared ctx->optp pointer, pass the context as a
constant pointer and use a local pointer (optp) for TCP option
traversal. This makes nf_osf_match_one() strictly stateless from the
caller's perspective, ensuring every fingerprint check starts at the
correct option offset.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 48% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
KE
Kernel · Linux
4.19.26 before 4.20; 4.20.13 before 5.0; 5.0.1 before 5.10.258; 5.11 before 5.15.209; 5.16 before 6.1.175; 6.2 before 6.6.141; +8 more · source: NVD
LI
Linux · Linux
1a6a0951fc009f6d9fe8ebea2d2417d80d54097b before 0145548346c4a30981a870a8ca00eac46ba27e85; 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b before 1c136f2c44a5913646bac85303612fd0825197a0; 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b before 1e19a07291bb8682c14c39a64725a3ae54ab8ccc; 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b before 32e50f92c7cf3f4eba29622179a5fcdc2aebab41; 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b before 70a3f31d25cf2ec9d4ddfa408120171ead955623; 1a6a0951fc009f6d9fe8ebea2d2417d80d54097b before 21883587593d7c8bb519a79460a0b5bc5ffbdabd; +7 more · source: vendor
SS
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP · Siemens
V3.1.6; V3.1.7; V3.1.6; V3.1.7 · source: CISA
SS
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP · Siemens
V3.1.6; V3.1.7; V3.1.6; V3.1.7 · source: CISA
SS
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP · Siemens
V3.1.6; V3.1.7 · source: CISA
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-52999
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-52999
Patch
https://git.kernel.org/stable/c/0145548346c4a30981a870a8ca00eac46ba27e85
Patch
https://git.kernel.org/stable/c/1c136f2c44a5913646bac85303612fd0825197a0
Patch
https://git.kernel.org/stable/c/1e19a07291bb8682c14c39a64725a3ae54ab8ccc
Patch
https://git.kernel.org/stable/c/21883587593d7c8bb519a79460a0b5bc5ffbdabd
Patch
https://git.kernel.org/stable/c/32e50f92c7cf3f4eba29622179a5fcdc2aebab41
Patch
https://git.kernel.org/stable/c/70a3f31d25cf2ec9d4ddfa408120171ead955623
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