Answer in brief
CVE-2026-31555 records a Medium severity (CVSS 5.5) vulnerability in futex: Clear stale exiting pointer in futex_lock_pi() retry path. 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-2026-31555 records a Medium severity (CVSS 5.5) vulnerability in futex: Clear stale exiting pointer in futex_lock_pi() retry path. 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 | >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <e7824ec168d2ac883a213cd1f4d6cc0816002a85 || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <5e8e06bf8909e79b4acd950cf578cfc2f10bbefa || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <de7c0c04ad868f2cee6671b11c0a6d20421af1da || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <7475dfad10a05a5bfadebf5f2499bd61b19ed293 || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <92e47ad03e03dbb5515bdf06444bf6b1e147310d || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <71112e62807d1925dc3ae6188b11f8cfc85aec23 || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <210d36d892de5195e6766c45519dfb1e65f3eb83 || f2a9957e5c08b1b1caacd18a3dc4c0a1bdb7b463 || cf16e42709aa86aa3e37f3acc3d13d5715d90096 || 61fa9f167caaa73d0a7c88f498eceeb12c6fa3db || 7874eee0130adf9bee28e8720bb5dd051089def3 || fc3b55ef2c840bb2746b2d8121a0788de84f7fac || >=4.4.255 <4.5 || >=4.9.255 <4.10 || >=4.14.158 <4.15 || >=4.19.172 <4.20 || >=5.4.1 <5.5 | 33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa, e7824ec168d2ac883a213cd1f4d6cc0816002a85, 5e8e06bf8909e79b4acd950cf578cfc2f10bbefa, de7c0c04ad868f2cee6671b11c0a6d20421af1da, 7475dfad10a05a5bfadebf5f2499bd61b19ed293, 92e47ad03e03dbb5515bdf06444bf6b1e147310d, 71112e62807d1925dc3ae6188b11f8cfc85aec23, 210d36d892de5195e6766c45519dfb1e65f3eb83, 4.5, 4.10, 4.15, 4.20, 5.5 |
| Linux/Linuxgeneric | 5.5 | 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 24, 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: futex: Clear stale exiting pointer in futex_lock_pi() retry path Fuzzying/stressing futexes triggered: WARNING: kernel/futex/core.c:825 at wait_for_owner_exiting+0x7a/0x80, CPU#11: futex_lock_pi_s/524 When futex_lock_pi_atomic() sees the owner is exiting, it returns -EBUSY and stores a refcounted task pointer in 'exiting'. After wait_for_owner_exiting() consumes that reference, the local pointer is never reset to nil. Upon a retry, if futex_lock_pi_atomic() returns a different error, the bogus pointer is passed to wait_for_owner_exiting(). CPU0 CPU1 CPU2 futex_lock_pi(uaddr) // acquires the PI futex exit() futex_cleanup_begin() futex_state = EXITING; futex_lock_pi(uaddr) futex_lock_pi_atomic() attach_to_pi_owner() // observes EXITING *exiting = owner; // takes ref return -EBUSY wait_for_owner_exiting(-EBUSY, owner) put_task_struct(); // drops ref // exiting still points to owner goto retry; futex_lock_pi_atomic() lock_pi_update_atomic() cmpxchg(uaddr) *uaddr ^= WAITERS // whatever // value changed return -EAGAIN; wait_for_owner_exiting(-EAGAIN, exiting) // stale WARN_ON_ONCE(exiting) Fix this by resetting upon retry, essentially aligning it with requeue_pi.
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 | >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <e7824ec168d2ac883a213cd1f4d6cc0816002a85 || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <5e8e06bf8909e79b4acd950cf578cfc2f10bbefa || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <de7c0c04ad868f2cee6671b11c0a6d20421af1da || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <7475dfad10a05a5bfadebf5f2499bd61b19ed293 || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <92e47ad03e03dbb5515bdf06444bf6b1e147310d || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <71112e62807d1925dc3ae6188b11f8cfc85aec23 || >=3ef240eaff36b8119ac9e2ea17cbf41179c930ba <210d36d892de5195e6766c45519dfb1e65f3eb83 || f2a9957e5c08b1b1caacd18a3dc4c0a1bdb7b463 || cf16e42709aa86aa3e37f3acc3d13d5715d90096 || 61fa9f167caaa73d0a7c88f498eceeb12c6fa3db || 7874eee0130adf9bee28e8720bb5dd051089def3 || fc3b55ef2c840bb2746b2d8121a0788de84f7fac || >=4.4.255 <4.5 || >=4.9.255 <4.10 || >=4.14.158 <4.15 || >=4.19.172 <4.20 || >=5.4.1 <5.5 | 33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa, e7824ec168d2ac883a213cd1f4d6cc0816002a85, 5e8e06bf8909e79b4acd950cf578cfc2f10bbefa, de7c0c04ad868f2cee6671b11c0a6d20421af1da, 7475dfad10a05a5bfadebf5f2499bd61b19ed293, 92e47ad03e03dbb5515bdf06444bf6b1e147310d, 71112e62807d1925dc3ae6188b11f8cfc85aec23, 210d36d892de5195e6766c45519dfb1e65f3eb83, 4.5, 4.10, 4.15, 4.20, 5.5 |
| Linux/Linuxgeneric | 5.5 | 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 24, 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: futex: Clear stale exiting pointer in futex_lock_pi() retry path Fuzzying/stressing futexes triggered: WARNING: kernel/futex/core.c:825 at wait_for_owner_exiting+0x7a/0x80, CPU#11: futex_lock_pi_s/524 When futex_lock_pi_atomic() sees the owner is exiting, it returns -EBUSY and stores a refcounted task pointer in 'exiting'. After wait_for_owner_exiting() consumes that reference, the local pointer is never reset to nil. Upon a retry, if futex_lock_pi_atomic() returns a different error, the bogus pointer is passed to wait_for_owner_exiting(). CPU0 CPU1 CPU2 futex_lock_pi(uaddr) // acquires the PI futex exit() futex_cleanup_begin() futex_state = EXITING; futex_lock_pi(uaddr) futex_lock_pi_atomic() attach_to_pi_owner() // observes EXITING *exiting = owner; // takes ref return -EBUSY wait_for_owner_exiting(-EBUSY, owner) put_task_struct(); // drops ref // exiting still points to owner goto retry; futex_lock_pi_atomic() lock_pi_update_atomic() cmpxchg(uaddr) *uaddr ^= WAITERS // whatever // value changed return -EAGAIN; wait_for_owner_exiting(-EAGAIN, exiting) // stale WARN_ON_ONCE(exiting) Fix this by resetting upon retry, essentially aligning it with requeue_pi.
Quoted source text, attributed separately from HOL analysis.