Answer in brief
CVE-2026-31427 records a Medium severity (CVSS 5.5) vulnerability in netfilter: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp. 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-2026-31427 records a Medium severity (CVSS 5.5) vulnerability in netfilter: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp. 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 | >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <faa6ea32797a1847790514ff0da1be1d09771580 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <82baeb871e8f04906bc886273fdf0209e1754eb3 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <6e5e3c87b7e6212f1d8414fc2e4d158b01e12025 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <fe463e76c9b4b0b43b5ee8961b4c500231f1a3f6 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <7edca70751b9bdb5b83eed53cde21eccf3c86147 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <01f34a80ac23ae90b1909b94b4ed05343a62f646 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <52fdda318ef2362fc5936385bcb8b3d0328ee629 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <6a2b724460cb67caed500c508c2ae5cf012e4db4 | faa6ea32797a1847790514ff0da1be1d09771580, 82baeb871e8f04906bc886273fdf0209e1754eb3, 6e5e3c87b7e6212f1d8414fc2e4d158b01e12025, fe463e76c9b4b0b43b5ee8961b4c500231f1a3f6, 7edca70751b9bdb5b83eed53cde21eccf3c86147, 01f34a80ac23ae90b1909b94b4ed05343a62f646, 52fdda318ef2362fc5936385bcb8b3d0328ee629, 6a2b724460cb67caed500c508c2ae5cf012e4db4 |
| Linux/Linuxgeneric | 2.6.26 | 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
Apr 13, 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: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp process_sdp() declares union nf_inet_addr rtp_addr on the stack and passes it to the nf_nat_sip sdp_session hook after walking the SDP media descriptions. However rtp_addr is only initialized inside the media loop when a recognized media type with a non-zero port is found. If the SDP body contains no m= lines, only inactive media sections (m=audio 0 ...) or only unrecognized media types, rtp_addr is never assigned. Despite that, the function still calls hooks->sdp_session() with &rtp_addr, causing nf_nat_sdp_session() to format the stale stack value as an IP address and rewrite the SDP session owner and connection lines with it. With CONFIG_INIT_STACK_ALL_ZERO (default on most distributions) this results in the session-level o= and c= addresses being rewritten to 0.0.0.0 for inactive SDP sessions. Without stack auto-init the rewritten address is whatever happened to be on the stack. Fix this by pre-initializing rtp_addr from the session-level connection address (caddr) when available, and tracking via a have_rtp_addr flag whether any valid address was established. Skip the sdp_session hook entirely when no valid address exists.
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 | >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <faa6ea32797a1847790514ff0da1be1d09771580 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <82baeb871e8f04906bc886273fdf0209e1754eb3 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <6e5e3c87b7e6212f1d8414fc2e4d158b01e12025 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <fe463e76c9b4b0b43b5ee8961b4c500231f1a3f6 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <7edca70751b9bdb5b83eed53cde21eccf3c86147 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <01f34a80ac23ae90b1909b94b4ed05343a62f646 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <52fdda318ef2362fc5936385bcb8b3d0328ee629 || >=4ab9e64e5e3c0516577818804aaf13a630d67bc9 <6a2b724460cb67caed500c508c2ae5cf012e4db4 | faa6ea32797a1847790514ff0da1be1d09771580, 82baeb871e8f04906bc886273fdf0209e1754eb3, 6e5e3c87b7e6212f1d8414fc2e4d158b01e12025, fe463e76c9b4b0b43b5ee8961b4c500231f1a3f6, 7edca70751b9bdb5b83eed53cde21eccf3c86147, 01f34a80ac23ae90b1909b94b4ed05343a62f646, 52fdda318ef2362fc5936385bcb8b3d0328ee629, 6a2b724460cb67caed500c508c2ae5cf012e4db4 |
| Linux/Linuxgeneric | 2.6.26 | 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
Apr 13, 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: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp process_sdp() declares union nf_inet_addr rtp_addr on the stack and passes it to the nf_nat_sip sdp_session hook after walking the SDP media descriptions. However rtp_addr is only initialized inside the media loop when a recognized media type with a non-zero port is found. If the SDP body contains no m= lines, only inactive media sections (m=audio 0 ...) or only unrecognized media types, rtp_addr is never assigned. Despite that, the function still calls hooks->sdp_session() with &rtp_addr, causing nf_nat_sdp_session() to format the stale stack value as an IP address and rewrite the SDP session owner and connection lines with it. With CONFIG_INIT_STACK_ALL_ZERO (default on most distributions) this results in the session-level o= and c= addresses being rewritten to 0.0.0.0 for inactive SDP sessions. Without stack auto-init the rewritten address is whatever happened to be on the stack. Fix this by pre-initializing rtp_addr from the session-level connection address (caddr) when available, and tracking via a have_rtp_addr flag whether any valid address was established. Skip the sdp_session hook entirely when no valid address exists.
Quoted source text, attributed separately from HOL analysis.