CVE-2026-31498

Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix ERTM re-init and zero pdu_len infinite loop l2cap_config_req() processes CONFIG_REQ for channels in BT_CONNECTED state to support L2CAP reconfiguration (e.g. MTU changes). However, since both CONF_INPUT_DONE and CONF_OUTPUT_DONE are already set from the initial configuration, the reconfiguration path falls through to l2cap_ertm_init(), which re-initializes tx_q, srej_q, srej_list, and retrans_list without freeing the previous allocations and sets chan->sdu to NULL without freeing the existing skb. This leaks all previously allocated ERTM resources. Additionally, l2cap_parse_conf_req() does not validate the minimum value of remote_mps derived from the RFC max_pdu_size option. A zero value propagates to l2cap_segment_sdu() where pdu_len becomes zero, causing the while loop to never terminate since len is never decremented, exhausting all available memory. Fix the double-init by skipping l2cap_ertm_init() and l2cap_chan_ready() when the channel is already in BT_CONNECTED state, while still allowing the reconfiguration parameters to be updated through l2cap_parse_conf_req(). Also add a pdu_len zero check in l2cap_segment_sdu() as a safeguard.

CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0001

Probability of exploitation

0.02%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-835 CWE-835

Affected Products

Vendor	Product	Versions
linux	linux_kernel	4.4.238 — 4.5
linux	linux_kernel	4.9.238 — 4.10
linux	linux_kernel	4.14.200 — 4.15
linux	linux_kernel	4.19.149 — 4.20
linux	linux_kernel	5.4.69 — 5.5
linux	linux_kernel	5.7.1 — 5.10.253
linux	linux_kernel	5.11 — 5.15.203
linux	linux_kernel	5.16 — 6.1.168
linux	linux_kernel	6.2 — 6.6.131
linux	linux_kernel	6.7 — 6.12.80
linux	linux_kernel	6.13 — 6.18.21
linux	linux_kernel	6.19 — 6.19.11
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/042e2cd4bb11e5313b19b87593616524949e4c52 https://git.kernel.org/stable/c/25f420a0d4cfd61d3d23ec4b9c56d9f443d91377 https://git.kernel.org/stable/c/52667c859fe33f70c2e711cb81bbd505d5eb8e75 https://git.kernel.org/stable/c/900e4db5385ec2cacd372345a80ab9c8e105b3a3 https://git.kernel.org/stable/c/9760b83cfd24b38caee663f429011a0dd6064fa9 https://git.kernel.org/stable/c/9a21a631ee034b1573dce14b572a24943dbfd7ae https://git.kernel.org/stable/c/de37e2655b7abc3f59254c6b72256840f39fc6d5 https://git.kernel.org/stable/c/e7aab23b7df89a3d754a5f0a7d2237548b328bd0

Frequently Asked Questions

What is CVE-2026-31498? +

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix ERTM re-init and zero pdu_len infinite loop l2cap_config_req() processes CONFIG_REQ for channels in BT_CONNECTED state to support L2CAP reconfiguration (e.g. MTU changes). However, since both CONF_INPUT_DONE and CONF_OUTPUT_DONE are already set from the initial configuration, the reconfiguration path falls through to l2cap_ertm_init(), which re-initializes tx_q, srej_q, srej_list, and retrans_list without freeing the previous allocations and sets chan->sdu to NULL without freeing the existing skb. This leaks all previously allocated ERTM resources. Additionally, l2cap_parse_conf_req() does not validate the minimum value of remote_mps derived from the RFC max_pdu_size option. A zero value propagates to l2cap_segment_sdu() where pdu_len becomes zero, causing the while loop to never terminate since len is never decremented, exhausting all available memory. Fix the double-init by skipping l2cap_ertm_init() and l2cap_chan_ready() when the channel is already in BT_CONNECTED state, while still allowing the reconfiguration parameters to be updated through l2cap_parse_conf_req(). Also add a pdu_len zero check in l2cap_segment_sdu() as a safeguard. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2026-31498? +

CVE-2026-31498 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0001, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-31498? +

CVE-2026-31498 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-31498? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-47066

Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in benoitc hackney allows Excessive Allocation. The Alt-Svc response header parser in …

CVE-2026-49017

In OpenStack Swift before 2.36.2 and 2.37.2, s3api middleware enters an infinite loop when processing a truncated aws-chunked PUT request …

CVE-2026-39806

Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in mtrudel bandit allows unauthenticated remote denial of service via worker process …

CVE-2025-27497

OpenDJ is an LDAPv3 compliant directory service. OpenDJ prior to 4.9.3 contains a denial-of-service (DoS) vulnerability that causes the server …

CVE-2025-29776

Azle is a WebAssembly runtime for TypeScript and JavaScript on ICP. Calling `setTimer` in Azle versions `0.27.0`, `0.28.0`, and `0.29.0` …

CVE-2025-32029

ts-asn1-der is a collection of utility classes to encode ASN.1 data following DER rule. Incorrect number DER encoding can lead …