Answer in brief
CVE-2026-43026 records a Medium severity (CVSS 5.5) vulnerability in netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
Answer in brief
CVE-2026-43026 records a Medium severity (CVSS 5.5) vulnerability in netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=076a0ca02644657b13e4af363f487ced2942e9cb <a5a89db6981a1ddf2314bf50cb49db5a3146185f || >=076a0ca02644657b13e4af363f487ced2942e9cb <1c2ebdeff8d088a2e47ae25d7b38447249adace2 || >=076a0ca02644657b13e4af363f487ced2942e9cb <a64b7bf84b4d5ea54218c5d374ec87fff9000f43 || >=076a0ca02644657b13e4af363f487ced2942e9cb <2898080c054ea4d6ddfaaf21bbedbc229a9a8376 || >=076a0ca02644657b13e4af363f487ced2942e9cb <fd002ff2ea030cbfb0188a11b3c60ce7f84485f4 || >=076a0ca02644657b13e4af363f487ced2942e9cb <929f7a9a7aad9404a5867216c3f8738232355b38 || >=076a0ca02644657b13e4af363f487ced2942e9cb <bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36 || >=076a0ca02644657b13e4af363f487ced2942e9cb <35177c6877134a21315f37d57a5577846225623e | a5a89db6981a1ddf2314bf50cb49db5a3146185f, 1c2ebdeff8d088a2e47ae25d7b38447249adace2, a64b7bf84b4d5ea54218c5d374ec87fff9000f43, 2898080c054ea4d6ddfaaf21bbedbc229a9a8376, fd002ff2ea030cbfb0188a11b3c60ce7f84485f4, 929f7a9a7aad9404a5867216c3f8738232355b38, bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36, 35177c6877134a21315f37d57a5577846225623e |
| Linux/Linuxgeneric | 3.4 | Not reported |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
Published upstream
May 1, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 14, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 14, 2026
In the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent ctnetlink_alloc_expect() allocates expectations from a non-zeroing slab cache via nf_ct_expect_alloc(). When CTA_EXPECT_NAT is not present in the netlink message, saved_addr and saved_proto are never initialized. Stale data from a previous slab occupant can then be dumped to userspace by ctnetlink_exp_dump_expect(), which checks these fields to decide whether to emit CTA_EXPECT_NAT. The safe sibling nf_ct_expect_init(), used by the packet path, explicitly zeroes these fields. Zero saved_addr, saved_proto and dir in the else branch, guarded by IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when NAT is enabled. Confirmed by priming the expect slab with NAT-bearing expectations, freeing them, creating a new expectation without CTA_EXPECT_NAT, and observing that the ctnetlink dump emits a spurious CTA_EXPECT_NAT containing stale data from the prior allocation.
Quoted source text, attributed separately from HOL analysis.
CVSS is 5.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=076a0ca02644657b13e4af363f487ced2942e9cb <a5a89db6981a1ddf2314bf50cb49db5a3146185f || >=076a0ca02644657b13e4af363f487ced2942e9cb <1c2ebdeff8d088a2e47ae25d7b38447249adace2 || >=076a0ca02644657b13e4af363f487ced2942e9cb <a64b7bf84b4d5ea54218c5d374ec87fff9000f43 || >=076a0ca02644657b13e4af363f487ced2942e9cb <2898080c054ea4d6ddfaaf21bbedbc229a9a8376 || >=076a0ca02644657b13e4af363f487ced2942e9cb <fd002ff2ea030cbfb0188a11b3c60ce7f84485f4 || >=076a0ca02644657b13e4af363f487ced2942e9cb <929f7a9a7aad9404a5867216c3f8738232355b38 || >=076a0ca02644657b13e4af363f487ced2942e9cb <bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36 || >=076a0ca02644657b13e4af363f487ced2942e9cb <35177c6877134a21315f37d57a5577846225623e | a5a89db6981a1ddf2314bf50cb49db5a3146185f, 1c2ebdeff8d088a2e47ae25d7b38447249adace2, a64b7bf84b4d5ea54218c5d374ec87fff9000f43, 2898080c054ea4d6ddfaaf21bbedbc229a9a8376, fd002ff2ea030cbfb0188a11b3c60ce7f84485f4, 929f7a9a7aad9404a5867216c3f8738232355b38, bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36, 35177c6877134a21315f37d57a5577846225623e |
| Linux/Linuxgeneric | 3.4 | Not reported |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
Published upstream
May 1, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 14, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 14, 2026
In the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent ctnetlink_alloc_expect() allocates expectations from a non-zeroing slab cache via nf_ct_expect_alloc(). When CTA_EXPECT_NAT is not present in the netlink message, saved_addr and saved_proto are never initialized. Stale data from a previous slab occupant can then be dumped to userspace by ctnetlink_exp_dump_expect(), which checks these fields to decide whether to emit CTA_EXPECT_NAT. The safe sibling nf_ct_expect_init(), used by the packet path, explicitly zeroes these fields. Zero saved_addr, saved_proto and dir in the else branch, guarded by IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when NAT is enabled. Confirmed by priming the expect slab with NAT-bearing expectations, freeing them, creating a new expectation without CTA_EXPECT_NAT, and observing that the ctnetlink dump emits a spurious CTA_EXPECT_NAT containing stale data from the prior allocation.
Quoted source text, attributed separately from HOL analysis.