Linux Kernel up to 5.13.5 netrom mod_timer operation after expiration

CVSS Meta Temp Score
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CTI Interest Score
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5.4$0-$5k0.00

Summaryinfo

A vulnerability has been found in Linux Kernel up to 5.13.5 and classified as problematic. Affected by this issue is the function mod_timer of the component netrom. This manipulation causes an unknown weakness. This vulnerability is tracked as CVE-2021-47294. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 5.13.5 and classified as problematic. Affected by this vulnerability is the function mod_timer of the component netrom. The CWE definition for the vulnerability is CWE-672. The product uses, accesses, or otherwise operates on a resource after that resource has been expired, released, or revoked. The impact remains unknown. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: netrom: Decrease sock refcount when sock timers expire Commit 63346650c1a9 ("netrom: switch to sock timer API") switched to use sock timer API. It replaces mod_timer() by sk_reset_timer(), and del_timer() by sk_stop_timer(). Function sk_reset_timer() will increase the refcount of sock if it is called on an inactive timer, hence, in case the timer expires, we need to decrease the refcount ourselves in the handler, otherwise, the sock refcount will be unbalanced and the sock will never be freed.

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2021-47294 since 05/21/2024. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 274749 (Ubuntu Pro FIPS 16.04 LTS : Linux kernel (FIPS) vulnerabilities (USN-7865-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 4.4.277, 4.9.277, 4.14.241, 4.19.199, 5.0, 5.4.136, 5.10.54 or 5.13.6 eliminates this vulnerability. Applying the patch 853262355518/a01634bf91f2/48866fd5c361/9619cc7d97c3/25df44e90ff5/6811744bd0ef/bc1660206c37/517a16b1a88b is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (274749). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.4

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔍

CVSSv2info

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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

Exploitinginfo

Class: Operation after expiration
CWE: CWE-672
CAPEC: 🔍
ATT&CK: 🔍

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

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Nessus ID: 274749
Nessus Name: Ubuntu Pro FIPS 16.04 LTS : Linux kernel (FIPS) vulnerabilities (USN-7865-1)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Upgrade: Kernel 4.4.277/4.9.277/4.14.241/4.19.199/5.0/5.4.136/5.10.54/5.13.6
Patch: 853262355518/a01634bf91f2/48866fd5c361/9619cc7d97c3/25df44e90ff5/6811744bd0ef/bc1660206c37/517a16b1a88b

Timelineinfo

05/21/2024 🔍
05/21/2024 +0 days 🔍
05/21/2024 +0 days 🔍
11/11/2025 +539 days 🔍

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2021-47294 (🔍)
GCVE (CVE): GCVE-0-2021-47294
GCVE (VulDB): GCVE-100-265387

Entryinfo

Created: 05/21/2024 17:16
Updated: 11/11/2025 22:52
Changes: 05/21/2024 17:16 (56), 06/23/2025 22:27 (13), 11/11/2025 22:52 (2)
Complete: 🔍
Cache ID: 216::103

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