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CVE-2026-63380

Libevent: Null Pointer Dereference in `evws_new_session`

5.7 Medium

Libevent is an event notification library. Prior to 2.2.2-alpha, libevent can dereference invalid list pointers in ws.c when evws_new_session enters its error path after evhttp_start_ws_ succeeds but bufferevent_enable_locking_ fails. evws_connection_free sees a non-null http_server and unconditionally calls TAILQ_REMOVE even though the session was never inserted into http_server->ws_sessions. A local caller able to induce this allocation or locking failure can crash the process. This issue is fixed in version 2.2.2-alpha.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
High
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.14%Unchanged since Aug 21, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.7

Libevent: Null Pointer Dereference in `evws_new_session`

Libevent is an event notification library. Prior to 2.2.2-alpha, libevent can dereference invalid list pointers in ws.c when evws_new_session enters its error path after evhttp_start_ws_ succeeds but bufferevent_enable_locking_ fails. evws_connection_free sees a non-null http_server and unconditionally calls TAILQ_REMOVE even though the session was never inserted into http_server->ws_sessions. A local caller able to induce this allocation or locking failure can crash the process. This issue is fixed in version 2.2.2-alpha.

Record
CVE-2026-63380
CVSS 4.0
5.7 MediumCVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-416, CWE-476
Updated
2026-11-02
EUVDEUVD-2026-63506 5.7

Libevent is an event notification library. Prior to 2.2.2-alpha, libevent can dereference invalid list pointers in ws.c when evws_new_session enters its error path after evhttp_start_ws_ succeeds but bufferevent_enable_locking_ fails. evws_connection_free sees a non-null http_server and unconditionally calls TAILQ_REMOVE even though the session was never inserted into http_server->ws_sessions. A local caller able to induce this allocation or locking failure can crash the process. This issue is fixed in version 2.2.2-alpha.

Record
EUVD-2026-63506
CVSS 4.0
5.7 MediumCVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02
NVD 5.7

Libevent is an event notification library. Prior to 2.2.2-alpha, libevent can dereference invalid list pointers in ws.c when evws_new_session enters its error path after evhttp_start_ws_ succeeds but bufferevent_enable_locking_ fails. evws_connection_free sees a non-null http_server and unconditionally calls TAILQ_REMOVE even though the session was never inserted into http_server->ws_sessions. A local caller able to induce this allocation or locking failure can crash the process. This issue is fixed in version 2.2.2-alpha.

Record
CVE-2026-63380
CVSS 4.0
5.7 MediumCVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Weakness
CWE-416, CWE-476
Updated
2026-11-02
OSV 5.7

Libevent: Null Pointer Dereference in `evws_new_session`

Libevent is an event notification library. Prior to 2.2.2-alpha, libevent can dereference invalid list pointers in ws.c when evws_new_session enters its error path after evhttp_start_ws_ succeeds but bufferevent_enable_locking_ fails. evws_connection_free sees a non-null http_server and unconditionally calls TAILQ_REMOVE even though the session was never inserted into http_server->ws_sessions. A local caller able to induce this allocation or locking failure can crash the process. This issue is fixed in version 2.2.2-alpha.

Record
CVE-2026-63380
CVSS 4.0
5.7 MediumCVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-416, CWE-476
Updated
2026-11-02
OSVUBUNTU-CVE-2026-63380 5.7

Libevent is an event notification library. Prior to 2.2.2-alpha, libevent can dereference invalid list pointers in ws.c when evws_new_session enters its error path after evhttp_start_ws_ succeeds but bufferevent_enable_locking_ fails. evws_connection_free sees a non-null http_server and unconditionally calls TAILQ_REMOVE even though the session was never inserted into http_server->ws_sessions. A local caller able to induce this allocation or locking failure can crash the process. This issue is fixed in version 2.2.2-alpha.

Record
UBUNTU-CVE-2026-63380
CVSS 4.0
5.7 MediumCVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02
OSVAZL-96912 No score

CVE-2026-63380 affecting package libtevent 0.14.1-1

Libevent is an event notification library. Prior to 2.2.2-alpha, libevent can dereference invalid list pointers in ws.c when evws_new_session enters its error path after evhttp_start_ws_ succeeds but bufferevent_enable_locking_ fails. evws_connection_free sees a non-null http_server and unconditionally calls TAILQ_REMOVE even though the session was never inserted into http_server->ws_sessions. A local caller able to induce this allocation or locking failure can crash the process. This issue is fixed in version 2.2.2-alpha.

Record
AZL-96912
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
libtevent
Azure Linux:3
through 0.14.1-1 None known
libevent
Ubuntu:Pro:14.04:LTS
All versions, plus listed versions
2.0.21-stable-12.0.21-stable-1ubuntu12.0.21-stable-1ubuntu1.14.04.12.0.21-stable-1ubuntu1.14.04.22.0.21-stable-1ubuntu1.14.04.2+esm12.0.21-stable-1ubuntu1.14.04.2+esm2
None known
libevent
Ubuntu:Pro:16.04:LTS
All versions, plus listed versions
2.0.21-stable-22.0.21-stable-2ubuntu0.16.04.12.0.21-stable-2ubuntu0.16.04.1+esm12.0.21-stable-2ubuntu0.16.04.1+esm2
None known
libevent
Ubuntu:Pro:18.04:LTS
All versions, plus listed versions
2.1.8-stable-42.1.8-stable-4build12.1.8-stable-4ubuntu0.1~esm12.1.8-stable-4ubuntu0.1~esm2
None known
libevent
Ubuntu:Pro:20.04:LTS
All versions, plus listed versions
2.1.8-stable-4build12.1.11-stable-1~exp02.1.11-stable-12.1.11-stable-1ubuntu0.1~esm12.1.11-stable-1ubuntu0.1~esm2
None known
libevent
Ubuntu:22.04:LTS
All versions, plus listed versions
2.1.12-stable-12.1.12-stable-1build12.1.12-stable-1build22.1.12-stable-1build32.1.12-stable-1ubuntu0.12.1.12-stable-1ubuntu0.2
None known
libevent
Ubuntu:24.04:LTS
All versions, plus listed versions
2.1.12-stable-92.1.12-stable-9ubuntu22.1.12-stable-9ubuntu2.12.1.12-stable-9ubuntu2.2
None known
libevent
Ubuntu:26.10
All versions, plus listed versions
2.1.12-stable-10build22.1.13-stable-1build1
None known
libevent
Ubuntu:26.04:LTS
All versions, plus listed versions
2.1.12-stable-10build12.1.12-stable-10build22.1.12-stable-10ubuntu0.12.1.12-stable-10ubuntu0.2
None known

History

History
RecordedChangedSources
first indexedCVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-63380 is a medium vulnerability (CVSS 5.7) in Libevent, published August 20, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.14%, the 3rd percentile. No source names a fixed version.

References

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