Answer in brief
CVE-2025-21731 records a High severity (CVSS 7.8) vulnerability in nbd: don't allow reconnect after disconnect. 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 1518F-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-2025-21731 records a High severity (CVSS 7.8) vulnerability in nbd: don't allow reconnect after disconnect. 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 1518F-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 1518F-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=b7aa3d39385dc2d95899f9e379623fef446a2acd <e70a578487a47d7cf058904141e586684d1c3381 || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <6bef6222a3f6c7adb6396f77f25a3579d821b09a || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <e3be8862d73cac833e0fb7602636c19c6cb94b11 || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <e7343fa33751cb07c1c56b666bf37cfca357130e || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <d208d2c52b652913b5eefc8ca434b0d6b757f68f || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739 || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302 || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <844b8cdc681612ff24df62cdefddeab5772fadf1 | e70a578487a47d7cf058904141e586684d1c3381, 6bef6222a3f6c7adb6396f77f25a3579d821b09a, e3be8862d73cac833e0fb7602636c19c6cb94b11, e7343fa33751cb07c1c56b666bf37cfca357130e, d208d2c52b652913b5eefc8ca434b0d6b757f68f, a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739, 9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302, 844b8cdc681612ff24df62cdefddeab5772fadf1 |
| Linux/Linuxgeneric | 4.12 | Not reported |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
Published upstream
Feb 27, 2025
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: nbd: don't allow reconnect after disconnect Following process can cause nbd_config UAF: 1) grab nbd_config temporarily; 2) nbd_genl_disconnect() flush all recv_work() and release the initial reference: nbd_genl_disconnect nbd_disconnect_and_put nbd_disconnect flush_workqueue(nbd->recv_workq) if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...)) nbd_config_put -> due to step 1), reference is still not zero 3) nbd_genl_reconfigure() queue recv_work() again; nbd_genl_reconfigure config = nbd_get_config_unlocked(nbd) if (!config) -> succeed if (!test_bit(NBD_RT_BOUND, ...)) -> succeed nbd_reconnect_socket queue_work(nbd->recv_workq, &args->work) 4) step 1) release the reference; 5) Finially, recv_work() will trigger UAF: recv_work nbd_config_put(nbd) -> nbd_config is freed atomic_dec(&config->recv_threads) -> UAF Fix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so that nbd_genl_reconfigure() will fail.
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 1518F-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=b7aa3d39385dc2d95899f9e379623fef446a2acd <e70a578487a47d7cf058904141e586684d1c3381 || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <6bef6222a3f6c7adb6396f77f25a3579d821b09a || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <e3be8862d73cac833e0fb7602636c19c6cb94b11 || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <e7343fa33751cb07c1c56b666bf37cfca357130e || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <d208d2c52b652913b5eefc8ca434b0d6b757f68f || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739 || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302 || >=b7aa3d39385dc2d95899f9e379623fef446a2acd <844b8cdc681612ff24df62cdefddeab5772fadf1 | e70a578487a47d7cf058904141e586684d1c3381, 6bef6222a3f6c7adb6396f77f25a3579d821b09a, e3be8862d73cac833e0fb7602636c19c6cb94b11, e7343fa33751cb07c1c56b666bf37cfca357130e, d208d2c52b652913b5eefc8ca434b0d6b757f68f, a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739, 9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302, 844b8cdc681612ff24df62cdefddeab5772fadf1 |
| Linux/Linuxgeneric | 4.12 | Not reported |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
Published upstream
Feb 27, 2025
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: nbd: don't allow reconnect after disconnect Following process can cause nbd_config UAF: 1) grab nbd_config temporarily; 2) nbd_genl_disconnect() flush all recv_work() and release the initial reference: nbd_genl_disconnect nbd_disconnect_and_put nbd_disconnect flush_workqueue(nbd->recv_workq) if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...)) nbd_config_put -> due to step 1), reference is still not zero 3) nbd_genl_reconfigure() queue recv_work() again; nbd_genl_reconfigure config = nbd_get_config_unlocked(nbd) if (!config) -> succeed if (!test_bit(NBD_RT_BOUND, ...)) -> succeed nbd_reconnect_socket queue_work(nbd->recv_workq, &args->work) 4) step 1) release the reference; 5) Finially, recv_work() will trigger UAF: recv_work nbd_config_put(nbd) -> nbd_config is freed atomic_dec(&config->recv_threads) -> UAF Fix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so that nbd_genl_reconfigure() will fail.
Quoted source text, attributed separately from HOL analysis.