Weakness (CWE)
CWE-364: Signal Handler Race Condition
The product uses a signal handler that introduces a race condition.
More detail
These issues occur when non-reentrant functions, or state-sensitive actions occur in the signal handler, where they may be called at any time. These behaviors can violate assumptions being made by the "regular" code that is interrupted, or by other signal handlers that may also be invoked. If these functions are called at an inopportune moment - such as while a non-reentrant function is already running - memory corruption could occur that may be exploitable for code execution. Another signal race condition commonly found occurs when free() is called within a signal handler, resulting in a double free and therefore a write-what-where condition. Even if a given pointer is set to NULL after it has been freed, a race condition still exists between the time the memory was freed and the pointer was set to NULL. This is especially problematic if the same signal handler has been set for more than one signal -- since it means that the signal handler itself may be reentered.
There are several known behaviors related to signal handlers that have received the label of "signal handler race condition":
- Shared state (e.g. global data or static variables) that are accessible to both a signal handler and "regular" code
- Shared state between a signal handler and other signal handlers
- Use of non-reentrant functionality within a signal handler - which generally implies that shared state is being used. For example, malloc() and free() are non-reentrant because they may use global or static data structures for managing memory, and they are indirectly used by innocent-seeming functions such as syslog(); these functions could be exploited for memory corruption and, possibly, code execution.
- Association of the same signal handler function with multiple signals - which might imply shared state, since the same code and resources are accessed. For example, this can be a source of double-free and use-after-free weaknesses.
- Use of setjmp and longjmp, or other mechanisms that prevent a signal handler from returning control back to the original functionality
- While not technically a race condition, some signal handlers are designed to be called at most once, and being called more than once can introduce security problems, even when there are not any concurrent calls to the signal handler. This can be a source of double-free and use-after-free weaknesses.
Signal handler vulnerabilities are often classified based on the absence of a specific protection mechanism, although this style of classification is discouraged in CWE because programmers often have a choice of several different mechanisms for addressing the weakness. Such protection mechanisms may preserve exclusivity of access to the shared resource, and behavioral atomicity for the relevant code:
- Avoiding shared state
- Using synchronization in the signal handler
- Using synchronization in the regular code
- Disabling or masking other signals, which provides atomicity (which effectively ensures exclusivity)
How to prevent it (3 mitigations)
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Requirements
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
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Architecture and Design
Design signal handlers to only set flags, rather than perform complex functionality. These flags can then be checked and acted upon within the main program loop.
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Implementation
Only use reentrant functions within signal handlers. Also, use validation to ensure that state is consistent while performing asynchronous actions that affect the state of execution.
Source: MITRE CWE-364
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High 7.8
zram: fix use-after-free in zram_bvec_write_partial()
In the Linux kernel, the following vulnerability has been resolved: zram: fix use-after-free in zram_bvec_write_partial() zram_read_page() picks the sync or async backing device read path based on whether the parent bio is NULL. zram_bvec_write_partial() pass…
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High 7.8CVE-2026-52910 Public exploit
bpf: Free reuseport cBPF prog after RCU grace period.
In the Linux kernel, the following vulnerability has been resolved: bpf: Free reuseport cBPF prog after RCU grace period. Eulgyu Kim reported the splat below with a repro. [0] The repro sets up a UDP reuseport group with a cBPF prog and replaces it with a new…
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High 7.8
ALSA: aloop: Fix peer runtime UAF during format-change stop
In the Linux kernel, the following vulnerability has been resolved: ALSA: aloop: Fix peer runtime UAF during format-change stop loopback_check_format() may stop the capture side when playback starts with parameters that no longer match a running capture strea…
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High 8.1
web_webview has a Race Condition vulnerability
in OpenHarmony v6.0 and prior versions allow a remote attacker arbitrary code execution in pre-installed apps.
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High 7.8
can: isotp: fix tx.buf use-after-free in isotp_sendmsg()
In the Linux kernel, the following vulnerability has been resolved: can: isotp: fix tx.buf use-after-free in isotp_sendmsg() isotp_sendmsg() uses only cmpxchg() on so->tx.state to serialize access to so->tx.buf. isotp_release() waits for ISOTP_IDLE via wait_e…
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High 7.5
Electron: Use-after-free in WebContents fullscreen, pointer-lock, and keyboard-lock permission callbacks
Electron is a framework for writing cross-platform desktop applications using JavaScript, HTML and CSS. Prior to versions 38.8.6, 39.8.0, 40.7.0, and 41.0.0-beta.8, apps that register an asynchronous session.setPermissionRequestHandler() may be vulnerable to …
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High 7.5
Race condition, use-after-free in the Graphics: WebRender component
Race condition, use-after-free in the Graphics: WebRender component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
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High 8.1
OpenSSH pre-authentication async signal safety issue
A signal handler in sshd(8) may call a logging function that is not async-signal-safe. The signal handler is invoked when a client does not authenticate within the LoginGraceTime seconds (120 by default). This signal handler executes in the context of the ssh…
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High 7.0CVE-2024-6409 EPSS 28%
Openssh: possible remote code execution due to a race condition in signal handling affecting red hat enterprise linux 9
A race condition vulnerability was discovered in how signals are handled by OpenSSH's server (sshd). If a remote attacker does not authenticate within a set time period, then sshd's SIGALRM handler is called asynchronously. However, this signal handler calls …
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High 8.1
Openssh: regresshion - race condition in ssh allows rce/dos
A security regression (CVE-2006-5051) was discovered in OpenSSH's server (sshd). There is a race condition which can lead sshd to handle some signals in an unsafe manner. An unauthenticated, remote attacker may be able to trigger it by failing to authenticate…
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High 7.5
Signal Handler Race Condition vulnerability in Mitsubishi Electric India GC-ENET-COM whose first 2 digits of 11-digit s…