Linux Kernel up to 7.0.9 net skb_try_coalesce infinite loop

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
7.1	$0-$5k	0.00

Summaryinfo

A vulnerability was found in Linux Kernel up to 7.0.9. It has been classified as critical. This vulnerability affects the function skb_try_coalesce of the component net. This manipulation causes infinite loop. This vulnerability is registered as CVE-2026-43503. No exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.0.9. It has been declared as critical. Affected by this vulnerability is the function skb_try_coalesce of the component net. The manipulation with an unknown input leads to a infinite loop vulnerability. The CWE definition for the vulnerability is CWE-835. The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. As an impact it is known to affect availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: net: skbuff: propagate shared-frag marker through frag-transfer helpers Two frag-transfer helpers (__pskb_copy_fclone() and skb_shift()) fail to propagate the SKBFL_SHARED_FRAG bit in skb_shinfo()->flags when moving frags from source to destination. __pskb_copy_fclone() defers the rest of the shinfo metadata to skb_copy_header() after copying frag descriptors, but that helper only carries over gso_{size,segs, type} and never touches skb_shinfo()->flags; skb_shift() moves frag descriptors directly and leaves flags untouched. As a result, the destination skb keeps a reference to the same externally-owned or page-cache-backed pages while reporting skb_has_shared_frag() as false. The mismatch is harmful in any in-place writer that uses skb_has_shared_frag() to decide whether shared pages must be detoured through skb_cow_data(). ESP input is one such writer (esp4.c, esp6.c), and a single nft 'dup to <local>' rule -- or any other nf_dup_ipv4() / xt_TEE caller -- is enough to land a pskb_copy()'d skb in esp_input() with the marker stripped, letting an unprivileged user write into the page cache of a root-owned read-only file via authencesn-ESN stray writes. Set SKBFL_SHARED_FRAG on the destination whenever frag descriptors were actually moved from the source. skb_copy() and skb_copy_expand() share skb_copy_header() too but linearize all paged data into freshly allocated head storage and emerge with nr_frags == 0, so skb_has_shared_frag() returns false on its own; they need no change. The same omission exists in skb_gro_receive() and skb_gro_receive_list(). The former moves the incoming skb's frag descriptors into the accumulator's last sub-skb via two paths (a direct frag-move loop and the head_frag + memcpy path); the latter chains the incoming skb whole onto p's frag_list. Downstream skb_segment() reads only skb_shinfo(p)->flags, and skb_segment_list() reuses each sub-skb's shinfo as the nskb -- both p and lp must carry the marker. The same omission also exists in tcp_clone_payload(), which builds an MTU probe skb by moving frag descriptors from skbs on sk_write_queue into a freshly allocated nskb. The helper falls into the same family and warrants the same fix for consistency; no TCP TX-side in-place writer is currently known to reach a user page through this gap, but a future consumer depending on the marker would regress silently. The same omission exists in skb_segment(): the per-iteration flag merge takes only head_skb's flag, and the inner switch that rebinds frag_skb to list_skb on head_skb-frags exhaustion does not fold the new frag_skb's flag into nskb. Fold frag_skb's flag at both sites so segments drawing frags from frag_list members carry the marker.

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2026-43503 since 05/01/2026. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 316553 (Debian dsa-6295 : ata-modules-6.12.74+deb13+1-armmp-di - security update), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.10.257, 5.15.208, 6.1.174, 6.6.141, 6.12.91, 6.18.33 or 7.0.10 eliminates this vulnerability. Applying the patch fbeab9555564a1b98e8582cd106dfe46c4606991/179f1852bdedc300e373e807cc102cd81feff196/12401fcfb01f53ccc63ab0a3246570fe8f3105ee/989214c66884d70716d83dc1d0bf5e16287bf349/fc6eb39c55e97df2f94ad974b8a5bbcd019da2c8/ff375cc75f9167168db38e0464a482d5fbc8d81d/9bc9d6d6967a2239aa57af2aa53554eddd640d20 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 databases at Tenable (316553) and EUVD (EUVD-2026-31536). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 5.10.256
• 5.15.207
• 6.1.173
• 6.6.140
• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
• 6.12.6
• 6.12.7
• 6.12.8
• 6.12.9
• 6.12.10
• 6.12.11
• 6.12.12
• 6.12.13
• 6.12.14
• 6.12.15
• 6.12.16
• 6.12.17
• 6.12.18
• 6.12.19
• 6.12.20
• 6.12.21
• 6.12.22
• 6.12.23
• 6.12.24
• 6.12.25
• 6.12.26
• 6.12.27
• 6.12.28
• 6.12.29
• 6.12.30
• 6.12.31
• 6.12.32
• 6.12.33
• 6.12.34
• 6.12.35
• 6.12.36
• 6.12.37
• 6.12.38
• 6.12.39
• 6.12.40
• 6.12.41
• 6.12.42
• 6.12.43
• 6.12.44
• 6.12.45
• 6.12.46
• 6.12.47
• 6.12.48
• 6.12.49
• 6.12.50
• 6.12.51
• 6.12.52
• 6.12.53
• 6.12.54
• 6.12.55
• 6.12.56
• 6.12.57
• 6.12.58
• 6.12.59
• 6.12.60
• 6.12.61
• 6.12.62
• 6.12.63
• 6.12.64
• 6.12.65
• 6.12.66
• 6.12.67
• 6.12.68
• 6.12.69
• 6.12.70
• 6.12.71
• 6.12.72
• 6.12.73
• 6.12.74
• 6.12.75
• 6.12.76
• 6.12.77
• 6.12.78
• 6.12.79
• 6.12.80
• 6.12.81
• 6.12.82
• 6.12.83
• 6.12.84
• 6.12.85
• 6.12.86
• 6.12.87
• 6.12.88
• 6.12.89
• 6.12.90
• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.18.14
• 6.18.15
• 6.18.16
• 6.18.17
• 6.18.18
• 6.18.19
• 6.18.20
• 6.18.21
• 6.18.22
• 6.18.23
• 6.18.24
• 6.18.25
• 6.18.26
• 6.18.27
• 6.18.28
• 6.18.29
• 6.18.30
• 6.18.31
• 6.18.32
• 7.0.0
• 7.0.1
• 7.0.2
• 7.0.3
• 7.0.4
• 7.0.5
• 7.0.6
• 7.0.7
• 7.0.8
• 7.0.9

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.2
VulDB Meta Temp Score: 7.1

VulDB Base Score: 5.7
VulDB Temp Score: 5.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 8.8
CNA Vector (Linux): 🔒

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

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

Exploitinginfo

Class: Infinite loop
CWE: CWE-835 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Nessus ID: 316553
Nessus Name: Debian dsa-6295 : ata-modules-6.12.74+deb13+1-armmp-di - security update

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.10.257/5.15.208/6.1.174/6.6.141/6.12.91/6.18.33/7.0.10
Patch: fbeab9555564a1b98e8582cd106dfe46c4606991/179f1852bdedc300e373e807cc102cd81feff196/12401fcfb01f53ccc63ab0a3246570fe8f3105ee/989214c66884d70716d83dc1d0bf5e16287bf349/fc6eb39c55e97df2f94ad974b8a5bbcd019da2c8/ff375cc75f9167168db38e0464a482d5fbc8d81d/9bc9d6d6967a2239aa57af2aa53554eddd640d20

Timelineinfo

05/01/2026 CVE reserved
05/23/2026 +22 days Advisory disclosed
05/23/2026 +0 days VulDB entry created
06/01/2026 +9 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-43503 (🔒)
GCVE (CVE): GCVE-0-2026-43503
GCVE (VulDB): GCVE-100-365335
EUVD: 🔒

Entryinfo

Created: 05/23/2026 15:57
Updated: 06/01/2026 08:53
Changes: 05/23/2026 15:57 (59), 05/23/2026 16:33 (1), 05/25/2026 20:22 (2), 06/01/2026 08:53 (12)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

Discussion

Do you want to use VulDB in your project?

Use the official API to access entries easily!