Answer in brief
CVE-2026-31680 records a High severity (CVSS 7.8) vulnerability in net: ipv6: flowlabel: defer exclusive option free until RCU teardown. 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-2026-31680 records a High severity (CVSS 7.8) vulnerability in net: ipv6: flowlabel: defer exclusive option free until RCU teardown. 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 7.8. 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 | >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <4b6798024f7b2d535f3db1002c760143cdbd1bd3 || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <3c54b66c83fb8fcbde8e6a7bf90b65856e39f827 || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <5a6b15f861b7c1304949e3350d23490a5fe429fd || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <6c7fbdb8ffde6413640de7cfbd7c976c353e89f8 || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <8027964931785cb73d520ac70a342a3dc16c249b || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <414726b69921fe6355ae453f5b35e68dd078342a || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <572ce62778519a7d4d1c15f55dd2e45a474133c4 || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <9ca562bb8e66978b53028fa32b1a190708e6a091 | 4b6798024f7b2d535f3db1002c760143cdbd1bd3, 3c54b66c83fb8fcbde8e6a7bf90b65856e39f827, 5a6b15f861b7c1304949e3350d23490a5fe429fd, 6c7fbdb8ffde6413640de7cfbd7c976c353e89f8, 8027964931785cb73d520ac70a342a3dc16c249b, 414726b69921fe6355ae453f5b35e68dd078342a, 572ce62778519a7d4d1c15f55dd2e45a474133c4, 9ca562bb8e66978b53028fa32b1a190708e6a091 |
| Linux/Linuxgeneric | 3.9 | 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 25, 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: net: ipv6: flowlabel: defer exclusive option free until RCU teardown `ip6fl_seq_show()` walks the global flowlabel hash under the seq-file RCU read-side lock and prints `fl->opt->opt_nflen` when an option block is present. Exclusive flowlabels currently free `fl->opt` as soon as `fl->users` drops to zero in `fl_release()`. However, the surrounding `struct ip6_flowlabel` remains visible in the global hash table until later garbage collection removes it and `fl_free_rcu()` finally tears it down. A concurrent `/proc/net/ip6_flowlabel` reader can therefore race that early `kfree()` and dereference freed option state, triggering a crash in `ip6fl_seq_show()`. Fix this by keeping `fl->opt` alive until `fl_free_rcu()`. That matches the lifetime already required for the enclosing flowlabel while readers can still reach it under RCU.
Quoted source text, attributed separately from HOL analysis.
CVSS is 7.8. 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 | >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <4b6798024f7b2d535f3db1002c760143cdbd1bd3 || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <3c54b66c83fb8fcbde8e6a7bf90b65856e39f827 || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <5a6b15f861b7c1304949e3350d23490a5fe429fd || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <6c7fbdb8ffde6413640de7cfbd7c976c353e89f8 || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <8027964931785cb73d520ac70a342a3dc16c249b || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <414726b69921fe6355ae453f5b35e68dd078342a || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <572ce62778519a7d4d1c15f55dd2e45a474133c4 || >=d3aedd5ebd4b0b925b0bcda548066803e1318499 <9ca562bb8e66978b53028fa32b1a190708e6a091 | 4b6798024f7b2d535f3db1002c760143cdbd1bd3, 3c54b66c83fb8fcbde8e6a7bf90b65856e39f827, 5a6b15f861b7c1304949e3350d23490a5fe429fd, 6c7fbdb8ffde6413640de7cfbd7c976c353e89f8, 8027964931785cb73d520ac70a342a3dc16c249b, 414726b69921fe6355ae453f5b35e68dd078342a, 572ce62778519a7d4d1c15f55dd2e45a474133c4, 9ca562bb8e66978b53028fa32b1a190708e6a091 |
| Linux/Linuxgeneric | 3.9 | 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 25, 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: net: ipv6: flowlabel: defer exclusive option free until RCU teardown `ip6fl_seq_show()` walks the global flowlabel hash under the seq-file RCU read-side lock and prints `fl->opt->opt_nflen` when an option block is present. Exclusive flowlabels currently free `fl->opt` as soon as `fl->users` drops to zero in `fl_release()`. However, the surrounding `struct ip6_flowlabel` remains visible in the global hash table until later garbage collection removes it and `fl_free_rcu()` finally tears it down. A concurrent `/proc/net/ip6_flowlabel` reader can therefore race that early `kfree()` and dereference freed option state, triggering a crash in `ip6fl_seq_show()`. Fix this by keeping `fl->opt` alive until `fl_free_rcu()`. That matches the lifetime already required for the enclosing flowlabel while readers can still reach it under RCU.
Quoted source text, attributed separately from HOL analysis.